CBSE Notes For Class 6 Science Chapter 5 Body Movements

Body Movements

The changing position of the body or any body part is called movement. It can involve the movement of a single body part (movement of the hand while writing), different parts of the body (during a workout), or the whole body (while walking).

Even when we are sitting still, many movements like blinking of eyes, beating of heart, etc. occur in our body, The Movement of animals from one place to another is known as locomotion.

There are different ways in which animals show locomotory movements like cows walking, snakes slithering, insects crawling, birds flying, fish swimming, etc. In this chapter, we will study the different movements that occur In different living organisms.

CBSE Notes For Class 6 Science Chapter 5 Body Movements

Human Body And Its Movements

Movement in human beings takes place with the help of the skeletal system (consisting of bones and cartilage) and muscular system (having muscles). Bone is the hard structural tissue that gives shape to our body. Our body consists of many bones.

The bones cannot be bent. We can bend our body part only at those points (places) where two or more bones are joined together. Muscles are attached to the bones. The contraction and relaxation of muscles bring about movement in the human body.

Read and Learn More Class 6 Science Notes

Joints Of The Body

The places where two or more bones meet are called joints. They allow body movements like bending and rotation of limbs, bending of back, and sideways movement of the neck.

Types Of Joints

Different types of joints are present in the human body that help us to carry out different movements and activities.

1. Freely Movable Joints

The joints in which one bone moves freely on the other are called freely movable joints. Such joints are found in the shoulder, hip, knee, elbow, ankle, and wrist.

Freely movable joints are of the following types

Ball and Socket Joint

The joints in which the rounded, ball-like end of one bone fits into the hollow part (socket) of the other bone are called ball and socket joints. The bone with the ball-like head is freely movable in all directions.

For example, the shoulder joint between the shoulder bone and the head of the upper arm bone and the hip joint, between the hip bone and thigh bone.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Ball And Socket Joint

Pivotal Joint

The joint in which the rounded surface of one bone fits into a ring formed by the other one is called the pivotal joint, for example joint between the neck and head. It allows us to bend our head forward and backward and turn right or left. It allows rotational movements only. In a pivotal joint, a cylindrical bone rotates in a ring.

 

CBSE Notes For Class 6 Science Chapter 5 Body Movements Pivotal Joint

Hinge Joints

The joints that allow movement of bones in only one direction, i.e. either forward or backward are called hinge joints. These joints allow movements like a hinge to its door shows movements. These are present in the elbow, knee, finger joints, and jaw.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Hinge Joints Of The Knee

Fixed Joints

The joints in which the bones are fixed and held so tightly that they cannot move at all are called fixed joints. These joints are also called immovable joints. For example, the bones ofour skull are held together tightly with such joints. Our upper jaw is also fixed to skull bones with the help of fixed joints.

CBSE Notes For Class 6 Science Chapter 5 Body Movements

Human Skeletal System

The bones (hard tissues) and cartilage (soft tissues) in our body form a framework that supports the whole body and gives a shape to it.

This framework is called the skeleton. The human skeleton is composed of around 305 bones at birth. The number of bones in the skeleton changes with age. It decreases to 206 bones by adulthood after some bones have fused.

CBSE Notes For Class 6 Science Chapter 5 Body Movements The Human Skeleton

Parts of the Skeleton System

The skeleton system consists of various bones. Some important bones are as follows

1. Skull

It is the bony part ofour head, which is made up of 22 skull bones. These are among the hardest bones ofour body. All the bones of the skull except the lower jaw are fixed.

It performs the following functions

  1. The skull protects the brain.
  2. It gives shape to our face and head.

CBSE Notes For Class 6 Science Chapter 5 Body Movements The skull

2. Ribcage

The ribs are the curved bones present in our chest region. Each rib is attached to the breast bone in front and the backbone at the back to form a box-like structure. This is called the ribcage. It is composed of12 pairs of ribs. All the ribs are joined to the backbone, but only a few ribs are attached to the chest or breast bone.

It performs the following functions

  1. The ribcage protects vital internal organs like the heart, lungs, and liver.
  2. It takes part in breathing movements along with the lungs.

CBSE Notes For Class 6 Science Chapter 5 Body Movements The Ribcage

3. Backbone

If we put a finger at the back of the neck and move it while pressing downwards, we can feel a long hard structure.

This is our backbone, which is a long, hollow, rod-like structure running from the neck to the hips. It is made up of 33 small bones that are placed over each other. Each small bone is called vertebrae.

CBSE Notes For Class 6 Science Chapter 5 Body Movements The Backbone

It performs the following functions

  1. The backbone provides major support to the body.
  2. It supports the head at its top.
  3. It attaches to the shoulder bones, ribs, and hip bones.

Science Insight Owl has 14 vertebrae in the neck region. This number is almost double the number present in humans. Due to this, the owl can turn its head up to 270 degrees.

4. Shoulder Bones

The arms of our body are attached to our shoulders. There are two shoulder bones, i.e. collar bones and shoulder blades. The bone in the upper arm fits into the socket of the shoulder blade (forming ball and socket joint).

CBSE Notes For Class 6 Science Chapter 5 Body Movements Shoulder Bones

It performs the following functions

  1. Collar bones on the two sides of the neck keep our shoulders apart.
  2. Shoulder blades connect the arms to the body

Pelvic Bones

The pelvic bone forms a large, basin-shaped framework at the lower end ofthe backbone, to which the legs are attached.

The pelvic bone is also known as the hip bone. This bone encloses the portion of the body below the stomach. It is also the part ofour skeleton, we sit on.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Pelvic Bones

It performs the following functions

  1. Pelvic bones protect and support the lower organs of the body.
  2. It attaches the legs to our body.

6. Bones of the Hand

Our hand is made up of three parts, i.e. wrist, palm, and fingers. The wrist is made up of several small bones called carpals that make the wrist flexible. Each finger is made up of three bones.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Bones Of The Hand

X-Ray Images of Our Bones

We can have some idea about the shape and number of bones in some parts ofour body by feeling them. The other way of knowing about bones is to look at X-ray images.

Sometimes when we are hurt or have an accident, doctors use these X-ray images to find out about any possible injuries that might have happened to the bones. The X-ray shows the shapes of the bones in our bodies.

CBSE Notes For Class 6 Science Chapter 5 Body Movements X-ray images of ankle and knee joints

Cartilage

These are the additional parts of the skeleton that are not as hard as the bones and can be bent easily. Most ofthe skeleton is made up of bones, but it has some cartilage too. Cartilage is a kind of soft and elastic tissue present in the following parts ofour body.

  1. It is present in the pinna of the ears (upper part).
  2. It is present at the tip of the nose.
  3. It is present (as cartilage discs) between the vertebrae of the backbone.
  4. It is present at the end of bones, i.e. the point where one bone joins the other at a joint.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Upper part pinna of ear has cartilage ear lobe no cartilage

Muscles

Bones cannot move by themselves. The muscles attached to the bones make them move at joints.

Contraction and relaxation of muscles make the bone move up and down. You can observe the contraction of muscles in your leg when you walk or run. When contracted, the muscle becomes shorter, stiffer, and thicker.

It thus, pulls the bone. Muscles work in pairs. When one of them contracts, the bone is pulled in that direction.

At the same time, the other member of the pair relaxes. To move the bone in the opposite direction, the relaxed muscle contracts to pull the bone towards its original position, while the first axes.

A muscle can only pull. It cannot be posh. Thus, two muscles have to work together to move a bone. For example, the up and down movements ofour arms are controlled by two muscles namely, the biceps and triceps.

When we want to raise our arm, the biceps in front contract, Le. become shorter to pull up the arm. To lower the arm, the triceps at the back contract and pull it down.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Two Muscles work together to move a bone

Gait Of Animals

Different animals use different organs to move from one place to another. So, the manner of movement, i.e. the gait also differs in different animals, for example, birds-fly, fish-swim, and snakes-crawl. We will discuss some ofthese movements in detail.

1. Earthworm

An earthworm does not have legs and bones. The body of an earthworm is made up of many rings that are joined end to end. It moves by alternate expansion and contraction of the body, that is by the muscles.

Movement in Earthworm

  1. An earthworm first extends the front part of the body, keeping the rear portion fixed to the ground.
  2. Then it fixes the front end and releases the rear end. After releasing the rear end, it then shortens the body and pulls the rear end forward. This makes it move forward by a small distance.
  3. In this process, the large number of minute movable bristles connected to the muses help in gripping the ground. These bristles are hair-like structures projecting out of the body of the earthworm.
  4. Earthworm’s body also secretes a slimy substance that helps in its movement by reducing friction Thus, by the repeated expansion and contraction of muses, earthworm moves through the soil.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Movement Of Earthworms

Science Insight The earthworm eats its way through the soil. Its body then throws away the undigested part of the material that it eats. This activity of an earthworm makes the soil fertile and more useful for plants.

Snail

The body of a snail is soft and consists of a head, foot, and shell. The shell is the outer skeleton of a snail which is not made up of bones. It is a single unit and does not help in its movement. The foot of a snail is a large, thick structure made up of strong muscles.

Movement in Snail

  1. Movement in snails occurs with the help of a muscular Shell Hegd wide foot. The contraction and relaxation of muscles push the body of the snail forward. However, the Slimy surface movement of the foot is slow A snal1 and is controlled by the muscles attached to it.
  2. The foot secretes a slimy substance which helps the snail to slide over the ground and drag its heavy shell with it.

CBSE Notes For Class 6 Science Chapter 5 Body Movements A snail

Science Insight Snails are commonly known as belly-footed animals. The broad flat muscular foot runs along its belly and is used for support and to carry out movement.’

Cockroach

A cockroach can walk, climb, and fly upto a short distance. It has an exoskeleton that covers the outer body. This outer (or exo) skeleton is made up of some plates joined together. These plates permit the movement of the cockroach body.

Movement in Cockroach

  1. It has three pairs of jointed legs attached to the breast region which help them to walk.
  2. Its legs have distinct muscles that move the legs for walking and climbing.
  3. Its wings are attached to the body muscles that help in the movement of wings as it flies.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Legs And Wings Of A Cockroach

Birds

The birds fly in the air and walk on the ground. The birds can fly as their bodies are well suited for flying. Some birds like ducks and swans can also swim in water.

Movement in Birds.

  • It has hind limbs (legs) for walking on the ground and wings for flying.
  • The birds fly in the air by moving their wings up and down continuously.
  • The main adaptations in the bodies of birds that enable them to fly are as follows
  • They have hollow and light bones which makes their bodies light
  • The bony parts of the forelimbs are modified to form wings for flying.
  • The breast bone is modified to hold the muscles of flight. These muscles are used to move the wings up and down during flight.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Structure of bird skeleton

Fish

Their body is like a boat, i.e. the head and tail are smaller than the middle portion. It is known as a streamlined body, i.e. body that tapers at both ends. This shape reduces friction in water and allows them to swim easily.

Movement in Fish

The skeleton of a fish is covered with strong muscles. Movement in fishes occurs due to the action of their muscles and fins.

  1. During swimming, the muscles make the front part of the body curve to one side, while the tail part swings towards the opposite side.
  2. The fish thus, forms a curve. Then quickly, the body and tail curve to the other side. This makes a jerk and pushes the body forward and helps in their movement. A series of such jerks make the fish swim ahead.
  3. Fish have several fins which helps them to keep the balance of the body. The fins also help to determine the direction, while swimming.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Movement In Fish

Snake

It has a long backbone which is very flexible. The body of a snake contains many thin muscles that are connected. These muscles also interconnect the backbone, ribs, and skin.

Movement in Snake

  1. The snake can curve its body into many loops. Each loop pushes the ground to give a forward push to the body against the ground.
  2. Since its long body makes many loops and each loop gives it a push, the snake moves very fast and not in a straight line. This kind of movement in a snake is called slithering.

CBSE Notes For Class 6 Science Chapter 5 Body Movements movement in snake

Yoga-For Better Health

Yoga is an invaluable gift of the ancient Indian tradition. The United Nations declared June 21 as the International Day of Yoga. Yoga helps in keeping the backbone erect and in relieving joint pain. Many postures in yoga require lifting of our body weight.

This helps in making the bones strong and preventing osteoporosis. Yoga keeps the heart healthy and helps it to work more efficiently. Thus, yoga keeps a person healthy. However, certain yoga postures should be performed under the supervision of a trained person.

Activity 1

Aim: To show that we can bend or rotate our body only at joints.

Materials Required: Scale or wooden stick and string.

Procedure:

  1. Straighten your right arm. Place a light wooden stick lengthwise on your arm so that your elbow is in the center.
  2. Ask your friend to tie the wooden stick with the arm at both ends by using a string.
  3. Now try to bend your arm at the elbow.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Arm can bend at elbow because bones form a joint at the elbow

Observation: Since a wooden stick is tied at the joint of the elbow you will not be able to bend your arm.

Conclusion: This activity shows that we can bend or move our body parts only at those places where two or more bones are joined together. These places are called joints.

Activity 2

Aim: To make a ball and socket joint.

Materials Required: Old rubber or plastic ball paper, bowl, Knife/scissors.

Procedure:

  1. Roll a strip of paper into a cylinder.
  2. Make a small hole in an old rubber or plastic ball.
  3. Push the paper cylinder into it.
  4. Put the ball in a small bowl.
  5. The ball and socket joint is ready.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Making A ball And Socket Joint

Observation: In this type of joint, the rounded end of one bone fits into the cavity of the other bone. It allows movement in all directions.

Conclusion: From this activity, it can be concluded that this joint is a ball and socket joint.

Activity 3

Aim: To show that hinge joints allow movement only in one plane and only upto 180°.

Materials Required: Cardboard or thickchart paper and pencil.

Procedure:

  1. Make a cylinder with cardboard or thick chart paper.
  2. Attach a small pencil to the cylinder by piercing the cylinder at the center.
  3. Now make a hollow half-cylinder in such a way that the rolled-up cylinder fits inside the half-cylinder easily.

CBSE Notes For Class 6 Science Chapter 5 Body Movements Directions Of Movement Allowed By A Hinge- Like

Observation: The hollow half cylinder with the rolled-up cylinder sitting inside it allows movement like a hinge.

Conclusion: From this activity, it can be concluded that hinge joints allow movement only in one plane and upto 180°.

Activity 4

Aim: To observe how an earthworm moves.

Materials Required: An earthworm, a piece of blotting or filter paper, smooth glass plate.

Procedure:

  1. Observe an earthworm moving on the soil in a garden.
  2. Gendy lifts it and places it on a piece of blotting or filter paper.
  3. Observe its movement.
  4. Then place it on a smooth glass plate or any slippery surface.
  5. Observe its movement again.

Observations: We will observe that earthworms can move easily on the soil, but find it difficult to move on filter paper and glass plate.

Conclusion: This activity shows that an earthworm can move easily on the soil. It has a large number of tiny bristles (hair-like structures) under its body. These bristles help to get a good grip on the ground. It is difficult for it to move on paper and glass because it cannot get a grip on both of them.

Activity 5

Aim: To observe the movement of a snail.

Materials Required: Snail and a glass plate.

Procedure:

  1. Place a snail on a glass plate and observe it.
  2. When it starts moving, carefully lift the glass plate along with the snail above the level of your head.
  3. Observe the movement of the snail from beneath the glass plate.
  4. Now tilt the glass plate.

Observation: A thick structure and head may come out of an opening in the shell. The thick structure is its foot, which is made up of strong muscles. Conclusion This activity shows the wavy motion ofthe snail’s foot.

Bones Of The Skull Notes

Bones Of The Skull Mandible

The mandible is the bone of the lower jaw.

General Features of Mandible Body

Mandible Body

The body is U-shaped and has two surfaces and two borders. It consists of right and left halves united in the median plane at the symphysis menti. The symphysis menti is a faint ridge on the upper part of the midline.

Mandible Body Upper Border

The upper border of the mandible is also known as alveolar border. It bears sockets for the teeth.

Mandible Body Lower Border

  • This border is also known as the base of the mandible. Posteriorly it is continuous with the lower border of the ramus of the mandible.
  • On either side of the midline, there is the presence of a digastric fossa for the attachment of the anterior belly of the digastric.

Bones Of The Skull The Mandible Of An Adult

Bones Of The Skull The lateral surface of one half of the mandible

Mandible Body External Surface

  • At the lower part of the midline (at symphysis menti) a triangular mental protuberance is present.
  • The upper angle of the triangle lies at the lower end of the symphysis menti.
  • The mental tubercles are present at the lower angles of this triangle.
  • A faint ridge is present on the external surface of the body extending upwards and backward from the mental tubercle up to the anterior margin of the ramus. This is called an oblique line.
  • The mental foramen, in an adult, is present below the second premolar tooth midway between the upper and lower borders.

Mandible Body Internal Surface

  • The mylohyoid line is oblique and extends diagonally downwards and forwards from just below the alveolar border (behind the 3rd molar tooth) to the lower part of symphysis menti.
  • The sublingual fossa is a smooth area above the anterior part of the mylohyoid line for the lodgement of the sublingual salivary gland.
  • The submandibular fossa is a concave area present below the posterior part of the mylohyoid line. It comes in contact with the superficial part of the submandibular gland.
  • The posterior part of the symphysis menti on either side of the midline presents a pair of elevations called superior and inferior genial tubercles. These tubercles are present above the anterior end of the mylohyoid line.

Read and Learn More Human Osteology Notes

Ramus of Mandible

The ramus of the mandible projects upwards from the posterior part of the body. It has four borders (anterior, posterior, upper, and lower), two surfaces (lateral and medial), and two processes (coronoid and condylar).

Bones Of The Skull The medial surface of one half of the mandible

Ramus of Mandible Borders

  • The upper border forms a notch, i.e., the mandibular notch. This border displays a triangular coronoid process anteriorly and a condylar process posteriorly.
  • The lower border is the backward continuation of the base of the body of the mandible.
  • The anterior border of the ramus is sharp and continuous below with the oblique line on the lateral surface of the body of the mandible.
  • The posterior border meets with the lower border of the ramus to form the angle of the mandible. This border is in continuation above with the condylar process

Ramus of Mandible Processes

  • The coronoid process is flat and triangular, which projects upwards from the anterosuperior part of the ramus. It lies at the junction of the upper (mandibular notch) and anterior border of the ramus.
  • The condylar process projects upwards from the posterosuperior part of the ramus.
  • The upper end of the condylar process is expanded and forms the head of the mandible. While the lower part of the condylar process is constricted and called the neck.
  • The head of the mandible bears an articular surface that articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint.
  • The anterior surface of the neck shows a depression called pterygoid fovea for attachment of lateral pterygoid muscle.

Ramus of Mandible Surfaces

  • The lateral surface is rough and flat in its anteroinferior part for the attachment of the masseter.
  • The medial surface presents a mandibular foramen close to its center. It leads into a mandibular canal which opens at the mental foramen.
  • The lingula is a tongue-shaped projection near the anterior margin of the mandibular foramen. There is the presence of a mylohoid groove just behind the lingula.
  • This groove runs forward and downwards from the mandibular foramen to the inner surface of the body of the mandible.
  • The area above the angle of the mandible is rough for the attachment of the medial pterygoid muscle.

Particular Features of Mandible Body

Attachments of muscles are shown for the external surface and internal surface. Relations of nerves, blood vessels, glands, and ligaments.

Mandible Body Ossification

  • The part of the bone between the mental foramen and mandibular foramen ossifies in the membrane (fibrous envelop of the Meckel’s cartilage of the first branchial arch).
  • The part of the body in front of the mental foramen and the part of the ramus above the mandibular foramen ossify in cartilage.
  • Each half was replaced by a bony union at the end of the first year of postnatal mandible ossifying in 6th week of IUL.
  • At birth, the mandible consists of two halves of the mandibular body united by the fibrous joint at symphysis menti. This fibrous joint is aged.

Bones Of The Skull The Attachments Of Muscles On The External Surface Of Mandible

Bones Of The Skull Attachments of muscles on the internal surface of mandible

Bones Of The Skull Relations Of Nerves, Blood Vessels, Glands And Ligamnets On The Medical Aspect Of Mandible

Bones Of The Skull The Ossification Of Left Half Of Mandible

Age Changes In Mandible

The bony features of the mandible change with age (children, adults, and old age).

Bones Of The Skull Age Chnages In Mandible

Bones Of The Skull Internal Surface Of Body And Ramus Of Mandible

Bones Of The Skull Inferior Surface of Frontal Bone

Frontal Bone

  • The frontal bone forms most of the part of the anterior cranial fossa. The bone consists of squamous (main) parts and orbital parts.
  • The squamous part forms the forehead and orbital parts form the major part of the roof of each orbit.

Frontal Bone Squamous (Main) Part

This part of the bone has an external surface and internal surface, right and left temporal surface, nasal part, and zygomatic processes.

Frontal Bone External Surface

  • The external surface of the squamous part forms the forehead. This surface presents frontal eminence about 3 cm above the supraorbital margin.
  • The other features seen on this surface are the glabella, superciliary arches, and supraorbital margins.
  • The supraorbital notch or foramen is seen on the supraorbital margin. Occasionally the metopic suture may be seen in the region of the glabella.

Frontal Bone Temporal Surface

This forms a small surface on the right and left sides below the temporal lines

Frontal Bone Internal Surface

  • This surface is concave and shows the impressions of cerebral sulci and gyri.
  • It shows a median groove (sagittal sulcus) for the superior sagittal sinus.
  • At the anterior end of the groove, there is the presence of a median ridge called the frontal crest. Just below the frontal crest is the presence of foramen caecum.

Frontal Bone Nasal Part

  • The nasal part is the downward projection of the squamous part of bone between two superior orbital margins.
  • The lower serrated margin of this part is concave downwards and known as the nasal notch.
  • The nasal notch bears a median projection, the nasal spine which articulates with the nasal bones in front and behind with the perpendicular plate of the ethmoid.
  • From medial to lateral, the nasal bone, frontal process of maxilla, and lacrimal bone articulate with each half of the nasal notch.

Bones Of The Skull Frontal Bone As Seen From External Aspect

Zygomatic Process

The zygomatic process passes downwards and laterally from the lateral end of the superior orbital margin.

The Orbital Part

The orbital part consists of right and left orbital plates separated from each other by a wide notch called an ethmoid notch.

  • The notch is occupied by the ethmoid bone.
  • The orbital surface faces downwards. It is smooth and forms the roof of the orbit.
  • The inferior aspect of the orbital plate, just lateral to a notch, shows the depressions of ethmoidal air cells. More anteriorly it shows the opening of the frontal air sinus.
  • There is the presence of lacrimal fossa at its anterolateral angle.
  • The trochlear fovea is present, at its anteromedial part.
  • The upper surface of the orbital plate forms the floor of the anterior cranial fossa and shows the impressions for sulci and gyri.

Articulations of the Frontal Bone

The following bones articulate with the squamous part of the frontal bone:

  • Posteriorly: Parietal bones (at the coronal suture), greater wings of the sphenoid.
  • Anteriorly: Zygomatic bone, nasal bone, frontal process of maxilla, lacrimal bone, and perpendicular plate of the ethmoid.
  • The following bones articulate with the orbital part:
  • Posteriorly: Lesser wings of sphenoid.
  • Medially: Orbital plate of ethmoid.

Bones Of The Skull The External Surface Of Left Parietal Bone

Frontal Bone Ossification

  • It ossifies in the membrane.
  • Two halves of the frontal bone begin to fuse at the age of the first post-natal year. The fusion is completed by the end of eight years.
  • If the suture persists in adults then it is known as a metopic suture.

Bones Of The Skull The Ossification Of Frontal Bone

Parietal Bone

The parietal bones are quadrilateral in shape and form the roof and side walls of the cranial cavity.

Bones Of The Skull The External Surface Of Left Parietal Bone

Parietal Bones General Features

Each one has:

  • Four borders: Superior, inferior, anterior and posterior.
  • Two surfaces: External and internal.
  • Four angles: Anterosuperior, anteroinferior, posterosuperior and posteroinferior.

The external surface is convex. The external surface shows the parietal eminence, parietal foramen, and superior and inferior temporal lines.

On the concave internal surface, the vascular grooves (for middle meningeal vessels) run upwards and backward from the anteroinferior angle. A shallow groove for the sigmoid sinus is seen at its posteroinferior angle.

Bones Of The Skull The internal Surface Of Left Parietal Bone

Parietal Bones  Particular Features

The attachments and relations of the bone with the soft tissues

Bones Of The Skull Attachments On Left Parietal Bone

Parietal Bones  Articulations

Articulations of the parietal bone are shown in

Parietal Bones  Side Determination

Hold the bone in such a way that the convex external surface faces laterally. The angle showing the vascular groove at the internal surface should be kept antero-inferiorly.

Bones Of The Skull Blood Vessels And Sinus In Realtion To The Internal Surface Of Left Parietal Bone

Parietal Bones  Anatomical Position

The superior border should be kept towards the median plane, the antero-inferior angle downwards and forwards.

Bones Of The Skull Internal Surface Of The Left Parietal Bone

Bones Of The Skull Internal Surface Of The Occiptal Bone

Parietal Bones  Ossification

It ossifies in the membrane

Bones Of The Skull Ossification Of Parietal Bone

Parietal Bones Occipital Bone

  • This bone is present in the posterior part of the skull. The presence of the large foramen magnum helps in dividing the bone into four parts.
  • A part above and behind the foramen magnum is an expanded curved plate of bone, i.e., a squamous part. It shows a superior angle and two lateral angles.
  • The superior angle lies at lambda and each lateral angle at asterion.
  • A part in front of frame n magnum is called the basilar part.
  • A pair of condylar parts are present on either side of the foramen magnum.

Parietal Bones Anatomical Position

Hold the bone in such a way that the foramen magnum should lie in the horizontal plane and the basilar part should be directed forwards and upwards.

Bones Of The Skull Attachment Of MUscles On The Inferior Surface Of Occipital Bone

Parietal Bones General Features

Squamous Part

  • The squamous part shows a convex external and a concave internal surface: one superior angle two lateral angles and two borders i.e., lambdoid and mastoid borders.
  • The external surface shows the presence of the external occipital protuberance and external
    occipital crest.
  • The highest nuchal line and the superior nuchal line run laterally from the external occipital protuberance, on the right and left sides. The inferior nuchal line runs laterally from the middle of the external occipital crest.
  • The internal surface of the squamous part shows the presence of internal occipital protuberance in the middle.
  • A wide median groove for the superior sagittal sinus is present above the protuberance. Grooves for transverse sinuses are present on either side of the protuberance. An internal occipital crest runs downwards in the midline from the internal occipital protuberance.
  • Borders—The lambdoid border articulates with the parietal bone at the lambdoid suture and the mastoid border articulates with the mastoid bone at the occipito¬ mastoid suture.

Basilar Part of the Occipital Bone

  • It extends forward and upwards from the anterior margin of the foramen magnum. This part has three surfaces (anterior, superior, and inferior), and two lateral borders.
  • The anterior surface extends upto the body of the sphenoid bone and forms a primary cartilaginous joint (basi-sphenoid joint), which is replaced by the bone at about 25 years of age.
  • The superior surface slopes downwards and backward and forms a part of the clivus.
  • The inferior surface bears a pharyngeal tubercle The lateral border of the basilar part articulates with the posterior border of the petrous part of the temporal bone.

Bones Of The Skull The Internal Surface Of The Occiptital Bone

Bones Of The Skull Attachment Of MUscles On The Inferior Surface Of Occipital Bone

The Condylar Part of the Occipital Bone

  • It presents superior and inferior surfaces. The inferior surface of the condylar part presents an occipital condyle. The hypo-glossal or anterior condylar canal opens just above the anterolateral side of the occipital condyle.
  • Just behind the condyle is the condylar fossa, which may show the opening of the posterior condylar canal.
  • The jugular process is a quadrilateral plate present lateral to the posterior half of the occipital condyle.
  • The upper surface of the jugular process is deeply grooved for the sigmoid sinus. The superior surface of the condylar part shows a jugular tubercle.

The Foramen Magnum

For structures passing through the foramen magnum

Foramen Magnum Particular Features

The soft tissue relation

Foramen Magnum Articulations

The following bones articulate with the occipital bone:

  • Parietal (at lambdoid suture).
  • Mastoid (at occipitomastoid suture).
  • Sphenoid (at the basisphenoid suture, which gets ossified at about the age of 25 years).

Bones Of The Skull Dural Venous Sinuses In Relation To Squamous Part Of Occipital Bone

Foramen Magnum Ossification

The squamous part, above the highest nuchal line, ossifies in the membrane. The rest of the bone ossifies in cartilage.

The part above the highest nuchal line may not unite with the rest of the bone and is then called interparietal bone.

Bones Of The Skull The Ossification Of Occipital Bone

Bones Of The Skull Lateral Paltes lower half of central pieces

Zygomatic Bone

It is situated on the upper lateral part of the face and forms the prominence of the cheek. Each zygomatic bone has a body and two processes (a frontal and a temporal process)

Zygomatic Bone General Features

The frontal process is directed upwards to articulate with the zygomatic process of the frontal bone.

The temporal process extends backward to articulate with zygomatic process of the temporal bone and forms the zygomatic arch. Anteromedially the body articulates with the maxilla.

Bones Of The Skull The External Surface Of Left Zygomatic Bone

General Features Body

  • The body has three surfaces and five borders. The surfaces are lateral, temporal arid orbital, while bordes are anteroinferior, anterosuperior (orbital), posteromedial, posterosuperior and postero-inferior.
  • The lateral surface is convex and presents zygomaticofacial foramen. This surface forms the prominence of the cheek.
  • The orbital surface forms the part of the lateral wall and floor of the orbit. It has the zygomatico-orbital foramen.
  • The temporal surface is directed posteromedially. It forms the anterior wall of the temporal fossa. The zygomaticotemporal foramen is present on this surface.

Zygomatic Bone Particular Features

The attachments of muscles on the zygomatic bone.

The following bones articulate with the zygomatic bone:

  • Frontal, maxilla, greater wing of the sphenoid, and the zygomatic process of temporal.
  • Side Determination and Anatomical Position

Hold the bone in such a way that:

  • The frontal process should look upwards.
  • The smooth concave orbital margin should face upwards and medially.
  • The smooth lateral surface should face laterally.
  • The direction of the lateral surface will determine the side of the bone

Zygomatic Bone Ossification

The bone ossifies in the membrane

Bones Of The Skull Anterolateral aspect of left maxilla

Bones Of The Skull Medial aspect of left maxilla

Bones Of The Skull Ossification of zygomatic bone, sometimes a fissure Divides The Bone In Upper And Lower Parts

Maxilla

The right and left maxillae take part in the formation of the whole of the upper jaw and part of the hard palate.

Maxilla General Features

Each maxilla consists of a body and four processes, i.e., an alveolar process, a zygomatic process, a frontal process, and a palatine process.

General Features Body

The body is pyramidal and encloses a large maxillary air sinus. Inferiorly, the body bears an alveolar process for the attachment of teeth.

The body possesses four surfaces: anterolateral, posterior, orbital, and nasal.

Anterolateral Surface

It is directed forward and laterally. Above, the anterior surface is limited by the infra¬ orbital margin.

Medially, this surface presents a nasal notch. Below the infraorbital margin, the infraorbital foramen is present. This surface also presents canine eminence, incisive fossa, and canine fossa.

Posterior Surface

It faces backward and laterally. This surface forms the anterior wall of the infratemporal fossa hence, also known as the infratemporal surface.

Inferiorly, this surface shows the maxillary tuberosity, which articulates with the pyramidal process of the palatine bone. Posterior superior alveolar foramina are seen on the surface.

Bones Of The Skull The lateral aspect of left maxilla

Orbital Surface

It forms the major part of the floor of the orbit. Posteriorly, it forms the anteromedial border of the infraorbital fissure.

There is the presence of an infraorbital groove near the center of the orbital surface. This groove leads to the infraorbital canal anteriorly, which opens on the anterior surface as infraorbital foramen.

Nasal (Medial) Surface

  • This surface takes part in the formation of the lateral wall of the nasal cavity.
  • The maxillary air sinus opens on this surface as a large maxillary hiatus
  • Posterior to the hiatus there is a groove, which is converted into a greater palatine canal by the perpendicular plate of the palatine bone.
  • Anteroinferior to the hiatus is the area of the inferior meatus.
  • Superior to the inferior meatus is the nasolacrimal groove.
  • There is the presence of a ridge anterior to the nasolacrimal groove. It is called the conchal crest, which articulates with the inferior nasal concha.

Nasal (Medial) Surface Processes

Zygomatic Process This strong process extends laterally from the body to articulate with the body of the zygomatic bone.

Zygomatic Process – Frontal Process

It extends upwards and medially where its tip articulates with the nasal part of the frontal bone. Anteriorly this process articulates with the nasal bone and posteriorly with the lacrimal bone.

The label surface of this process has a ridge called as a lacrimal crest, The medial surface is marked by an ethmoidal cress.

Bones Of The Skull The medial aspect of left maxilla

Alveolar Process

It extends downwards and carries the sockets for the teeth of the upper jaw.

Palatine Process

It is a horizontal plate, that projects medially from the nasal surface of the body of the maxilla. Medially it articulates with the palatine process of the opposite maxilla to form the anterior % of the hard palate.

It has superior and inferior surfaces and two free borders, i.e., medial and posterior. Posteriorly, it articulates with the anterior border of the horizontal plate of the palatine bone.

Anatomical Position and Side Determination Mold the bone in such a way that:

  • The medial border of its palatine process should be in the median plane.
  • The frontal process should point upwards.
  • Zygomatic process laterally.

Ossification

It ossifies in the membrane from a single centre which appears in the 6th week of JUL.

Ethmoid

It is a single, irregular midline bone situated between two orbits, in the ethmoidal notch of the frontal bone.

The parts, of the ethmoid can be appreciated by seeing a coronal section of the bone. It consists of a midline perpendicular plate, and two cuboidal bony masses on either side (labyrinth), which are connected to the perpendicular plate by a horizontal cribriform plate.

Perpendicular Plate

At the upper end of the perpendicular plate crista galli is present. The crista galli is seen on the floor of the anterior cranial cavity.

The perpendicular plate takes part in the formation of the median nasal septum.

Labyrinths

The right and left labyrinths are fragile, pneumatic bone.

  • It consists of many small air spaces (ethmoidal air sinuses). The ethmoidal air sinuses are arranged in the anterior, middle, and posterior groups.
  • The walls of these air spaces are very thin and incomplete. The labyrinth is present between nasal and orbital cavities.
  • The medial wall of the labyrinth is a part of the lateral wall of the nasal cavity and is bounded by the medial plate.

Bones Of The Skull Superior aspect of ethmoid bone

Bones Of The Skull Superior aspect of sphenoid bone. Anterior clinoid process is bifid

From this medial plate, there arises superior and middle conchae. Deep to middle concha there is the presence of a hook-like uncinate process and a rounded elevation, the bulla ethmoidale

The lateral wall of the labyrinth is formed by the orbital plate. The orbital plate forms the part of the medial wall of the orbit.

Cribriform Plate

The cribriform plate is the horizontal plate with numerous perforations.

It connects the labyrinths with the median perpendicular plate. The cribriform plate is seen on the floor of the anterior cranial fossa on either side of the crista galli. It also forms the roof of the nasal cavity.

Articulations

  • The perpendicular plate articulates with vomer, septal cartilage, frontal, nasal, and sphenoid bone.
  • The cribriform plate articulates with the orbital plate and sphenoid bone.
  • Labyrinth articulates with frontal, sphenoid, maxilla, lacrimal, perpendicular plate of palatine, and inferior nasal concha.

Ossification

The ethmoid bone ossifies in a cartilaginous capsule. There appear three centers, i.e., one for the perpendicular plate and one each for the labyrinth. The centers for the labyrinth appear labyrinth. The centers for the labyrinth appear All centers unite to form a single bone by the end of the third year of age.

Palatine Bone

It is situated between the maxilla and pterygoid process. It is L-shaped in appearance and consists of perpendicular and horizontal plates. It also has three processes, pyramidal, orbital, and sphenoidal.

Horizontal Plate

The horizontal plate forms the posterior part plate of palatine and inferior nasal concha anterior, posterior, lateral, and medial. The posterior border is free and projects backward in the midline to form the posterior nasal spine.

Perpendicular Plate

  • It has two surfaces, maxillary and nasal, and four borders, i.e., anterior, posterior,
  • All centers unite to form a single bone by greater palatine which is converted into the greater palatine canal with the help of the maxilla. This surface also forms the medial wall of the pterygopalatine fossa.
  • The nasal is L-shaped in appearance (i.e., ethmoidal crest, which articulates with the middle concha of the ethmoid bone, and conchal crest articulates with the inferior concha).
  • The right and left pterygoid processes. The posterior border of the perpendicular plate articulates with the medial pterygoid Body plate.
  • The superior border of the perpendicular plate bears an orbital process and a sphenoidal process.
  • Between these two processes, there is the presence of a sphenopalatine notch, which is converted into sphenopalatine foramen with the body of the sphenoid.

Pyramidal Process

  • The pyramidal process is directed backward and laterally from the junction of horizontal and perpendicular plates.
  • This process fits into a pterygoid fissure of pterygoid processes. Its inferior surface presents lesser palatine foramina.

Orbital Process

It is present at the anterior end of the upper border of the perpendicular plate. It forms the posterior part of the floor of the orbit.

Sphenoidal Process

It is situated at the posterior end of the upper border of the perpendicular plate. This process is grooved to complete the palatinovaginal canal.

Sphenoid Bone

It is a single, irregular, pneumatic bone situated posterior to the ethmoid and frontal bone. It forms the middle part of the base of the skull.

Sphenoid Bone General Features

The sphenoid consists of:

  • A centrally placed body
  • A pair of greater and lesser wings.

Sphenoid Bone Body

  • The body of the sphenoid is cuboidal in shape and contains a pair of sphenoidal air sinuses. It has six surfaces (i.e., superior, inferior, anterior, posterior, and right and left lateral surfaces).
  • The superior surface of the body bears the hypophyseal fossa. It forms the posterior part of the anterior cranial fossa (jugum sphenoidale, sulcus chiasmaticus, and tuberculum sellae) and the central part of the middle cranial fossa (hypophyseal fossa, dorsum sellae, and posterior clinoid process).
  • The inferior swap of the body forms the posterior part of the roof of the nasal cavity and the roof of the nasopharynx. It shows a median ridge called a rostrum, which articulates with the grooved margin of the vomer.
  • The anterior surface of the sphenoid articulates with the ethmoid. It presents a median ridge called a sphenoidal crest for articulation with the perpendicular plate of the ethmoid bone. On either side of the crest lies a thin plate of bone called sphenoidal concha. The sphenoidal foramen lies above and medial to the concha.
  • The posterior surface is rough and articulates with the basilar part of the occipital bone.
  • The upper part of the lateral surface is seen in the floor of the middle cranial fossa and shows a shallow groove the carotid sulcus. The lower part of the lateral surface unites with the greater wing and medial pterygoid plate.

Bones Of The Skull The sphenoid bone

Sphenoid Bone Wings

Sphenoid Bone Greater Wings

  • Each greater wing has three surfaces, i.e., cerebral (upper), orbital, and lateral.
  • The cerebral surface forms a part of the middle cranial fossa and is related to the temporal lobe of the cerebrum.
  • Anteromedially, it has a sharp free margin, which forms the inferolateral boundary of the superior orbital fissure. This surface shows the presence of foramen rotundum, ovale, and spinosum.
  • The lateral surface of the greater wing of the sphenoid is divided into the upper temporal surface and lower infratemporal surface.
  • The infratemporal surface forms the roof of infratemporal fossa. This surface shows the opening of foramen ovale and spinosum.
  • This surface also shows the presence of the spine of the sphenoid, which is present posterolateral to the foramen spinosum. At the junction of the temporal and infratemporal surfaces, there is the presence of an infratemporal crest.
  • The orbital surface is quadrilateral in shape and forms part of the lateral wall of the orbit. This surface concerns the superior orbital fissure (above) and inferior orbital fissure.

Sphenoid Bone Lesser Wings

It extends laterally from the anterosuperior part of the body of the sphenoid.

  • It is connected to the body by anterior and posterior roots. In between the two roots and the body of the sphenoid, there is the presence of the optic canal.
  • The lesser wing consists of two surfaces (superior and inferior) and two borders (anterior and posterior).
  • The superior surface forms the posterior-most part of the floor of the anterior cranial fossa. The inferior surface forms the superior border, of the superior orbital fissure.
  • The anterior border articulates with the posterior border of the orbital plate, while the posterior border is free.
  • The medial end of the posterior border ends in the anterior clinoid process.

Bones Of The Skull Sphenoid bone as seen from anterior aspect

Bones Of The Skull External surface of right temporal bone

Pterygoid Processes

  • The pterygoid processes, on either side, extend downwards from the junction of the root of the greater wing and body of the sphenoid.
  • Each process consists of lateral and medial pterygoid plates, which are separated posteriorly from each other by pterygoid fossa.
  • Anteriorly both the plates are continuous with each other and form the posterior wall of the pterygopalatine fossa.
  • Following three foramina open anteriorly in the pterygoid process—foramen rotundum, pterygoid canal, and palatinovaginal canal

Sphenoid Bone Articulations

  • Body of sphenoid Ethmoid bone (anteriorly), basilar part of the occipital (posteriorly)
  • The lesser living of the Orbital plate of the frontal bone sphenoid anteriorly
  • Greater wing of Frontal bone (anterosphenoid medially)
  • Zygomatic bone (anterolaterally)
  • Parietal bone (superiorly)
  • Squamous temporal bone (posterolateral) Petrous temporal (posteriorly) Pterygoid process Maxilla (anteriorly) Perpendicular plate of palatine (Medial pterygoid plate)
  • Pyramidal process of palatine (Lower ends of pterygoid plates).

Sphenoid Bone Ossification

The sphenoid gets ossified partly in the membrane and partly in cartilage.

Sphenoid Bone Temporal Bone

The temporal bone is situated on each side of the base and side of the skull.

This bone consists of the following parts:

  • Squamous.
  • Petrosal.
  • Mastoid.
  • Tympanic.
  • Styloid process.

Sphenoid Bone Squamous Part

  • It is a thin plate-like bone. It forms the anterosuperior part of the bone. It has external (temporal) and internal (cerebral) surfaces and a superior and an anteroinferior border.
  • The external surface (on the lateral aspect) shows the zygomatic process, roots of the zygomatic process, supramastoid crest, temporal lines, and supra-meatal triangle.
  • The external surface (on the inferior aspect) is made up of a small infratemporal suiface, articular tubercle, mandibularfossa and scfuamotympanic fissure.
  • The internal or cerebral surface is concave and shows an impression of the gyri of the cerebrum and blood vessels.

Bones Of The Skull The lateral aspect of left temporal bone

Bones Of The Skull The lateral aspect ol left temporal bone

Mastoid Part of Sphenoid Bone

  • It lies posterior to the squamous part. It shows external and internal surfaces and a posterior border.
  • It bears a downward extending conical projection, the mastoid process.
  • The outer surface is smooth and may show the opening of the mastoid foramen near its posterior border.
  • The inner surface is marked by a vertical groove for the sigmoid sinus.
  • The medial surface of the mastoid process shows a deep groove called the mastoid notch and a shallow groove for the occipital artery.

Petrous Part of Sphenoid Bone

  • This part of the bone is triangular and present at the base of the skull.
  • It has a base, an apex, three borders (superior, anterior, and posterior), and three surfaces (anterior, posterior, and inferior). The bone contains the internal and middle ear cavities

Base of Sphenoid Bone

  • The base of the petrous bone is directed backward and laterally and fuses with the squamous and mastoid parts.

Apex of Sphenoid Bone

It is directed forward and medially. It forms the posterior margin of the foramen lacerum.

Borders of Sphenoid Bone

  • The superior border demarcates the middle cranial fossa from the posterior cranial fossa. It is grooved by the superior petrosal sinus.
  • The medial part of the anterior border articulates with the greater wing of the sphenoid and the lateral part fuses with the squamous part.
  • The medial part of the posterior border forms a sulcus for the inferior petrosal sinus.
  • The lateral part forms the boundary of the jugular foramen.

Surfaces of Sphenoid Bone

The anterior surface of the petrous bone forms the posterior wall of the middle cranial fossa and shows the following features from medial to the lateral side trigeminal impression, hiatus for greater petrosal nerve, hiatus for lesser petrosal nerve, arcuate imminence, and tegmen tympani.

The posterior surface forms the anterior wall of the posterior cranial fossa and shows the opening of the internal acoustic meatus.

The inferior surface of the petrous bone is rough and presents the lower opening of the carotid canal and depression of the jugular fossa in front of the jugular foramen.

The Tympanic Part of Sphenoid Bone

  • It is a curved plate of bone, situated anterior and inferior to the external acoustic meatus. It forms the non-articular posterior wall of the mandibular fossa.
  • This plate forms the anterior, inferior, and lower part of the posterior wall of the external acoustic meatus.
  • The superior border of the tympanic plate meets the squamous temporal bone at the squamotympanic fissure. The inferior border forms a sheath for the base of the styloid process.
  • The rough lateral margin of the tympanic plate gives attachment to the cartilaginous part of the external acoustic meatus.

The Styloid Process of Sphenoid Bone

The styloid process is a conical projection of about 2.5 cm long. It is present on the inferior aspect of the temporal bone.

It is directed downwards forward and medially. The root of the styloid process is ensheathed by the tympanic plate. The stylomastoid foramen is situated between the styloid and mastoid process.

Side Determination and Anatomical Position Hold the bone in such a way that:

  • The zygomatic process faces anteriorly.
  • External acoustic meatus laterally.
  • The mastoid process faces backward and downwards

Articulations of Sphenoid Bone

Squamous part – With greater wing of sphenoid anteriorly With the parietal bone superiorly With the head of the mandible at the temporomandibular joint.

Petrous part – With the greater wing of the sphenoid anteriorly With the occipital bone posteriorly

Mastoid part- With the parietal bone superiorly With the occipital bone posteriorly and medially.

Zygomatic Process- With the temporal process of zygomatic bone.

Bones Of The Upper Limb Notes

Bones Of The Upper limb

The Upper limb consists of many regions. The following bones are present in various regions of the upper limb

Pectoral Region

It consists of two bones on each side, i.e., clavicle and scapula. These two bones form the pectoral or shoulder girdle. The lateral end of the clavicle articulates with the scapula at the acromioclavicular joint.

The medial end of the clavicle articulates with the sternum (axial skeleton) through the sternoclavicular joint. Thus the pectoral girdle serves to attach the upper limb to the trunk.

Arm

This region consists of a single bone called as humerus. The upper end of this bone articulates with the scapula at the shoulder joint. The lower end of the humerus articulates with two long bones of the forearm, i.e., the radius and ulna at the elbow joint.

Upper Limb Bones

Forearm

The ulna is medial while the radius is laterally placed in the forearm. At their lower ends, they articulate with carpal bones to form wrist joints.

Hand

The skeleton of the hand consists of many bones ie., carpals, metacarpals, and phalanges. These bones form many joints i.e., intercarpal, sternal facet carpometacarpal, metacarpophalangeal, and interphalangeal joints.

Read and Learn More Human Osteology Notes

Bones Of The Upper Limb Schematic Diagram To Show The bones Of The Right Upper Limb

Bones form many joints i.e., intercarpal, sternal facet carpometacarpal, metacarpophalangeal, and interphalangeal joints.

The Clavicle or Clavicle Anatomy

Trapezoid The description of the bone in the following paragraph and the reference will help you to learn the “side determination” and “anatomical position” of bone.

costalFacet for cartilage first Subcostal groove Acromian facet The clavicle (collar bone) is a horizontal or inferior surface of a right-placed long bone, which shows two ends (medial and lateral) and a shaft.

Upper Limb Bones

Clavicle Bone

The medial end is thick and rounded Side Determination while the lateral end is broad and flattened. The shaft shows “S” shaped double curvatures, which meet each other at the junction of medial 2/3 and lateral 1/3 of the bone.

The medial 2/3 of the bone is cylindrical and convex forwards, while the lateral 1/3 of the shaft is flattened and concave forwards. The superior surface of the bone is smooth as it is subcutaneous.

On the other hand, the inferior surface is rough near its medial and lateral ends due to the attachment of ligaments. The inferior surface also shows the presence of a shallow groove in its middle third.

Bones Of The Upper Limb General Features Of Superior surface of right clavicle

 Clavicle Anatomy or Clavicle Side Determination

  • Hold the bone horizontally in such a way that its rounded thick end is nearer to the median plane (placed medially) and the flattened end is directed laterally.
  • Identify the rough inferior surface and smooth superior surface. Keep the inferior surface facing inferiorly (towards the ground).
  • The convexity of the medial 2/3 of the shaft should be directed anteriorly.
  • In this position, the lateral end will direct the side of the bone.

Clavicle Bone or Clavicle Anatomical Position

Hold the clavicle horizontally in such a way that its medial end is directed slightly forward and inferiorly as compared to its lateral end (which is directed upward and backward).

Clavicle General Features

For ease of understanding the clavicle is divided into medial 2/3 and lateral 1/3.

Medial 2/3 of Clavicle

Hold the bone in an anatomical position and note the following.

  1. It consists of a cylindrical shaft and a thick rounded medial (sternal) end.
  2. As the shaft is cylindrical borders are ill-defined (not well marked).
  3. There are four surfaces, i.e., superior, inferior, anterior, and posterior. In the absence of well-defined borders, these surfaces are continuous with each other.
  4. The superior surface is mostly smooth. It is covered by skin and platysma muscle.
  5. The anterior surface of the medial 2/3 of the clavicle is convex anteriorly.
  6. The posterior surface is smooth and concave posteriorly.

Clavicle Bone

Now turn the bone upside down to the clavicular joint. see the inferior surface.

  1. The inferior surface has a large rough Particular Features impression near its medial end, which gives attachment to a ligament.
  2. There is the presence of a shallow groove in the middle third of the inferior surface. This groove is known as the subclavian groove.

The medial end of the clavicle shows a large smooth saddle-shaped articular surface on its medial aspect (sternal surface), which also extends for a short distance on the inferior surface of the bone.

The medial end of the clavicle articulates with the manubrium sterni (at sternoclavicular joint) and also with the first costal cartilage near its inferior surface.

Lateral 1/3 of the Clavicle

As the lateral 1/3 of the clavicle is flat. It shows well-defined anterior and posterior sternohyoid borders and superior and inferior surfaces.

  • Hold the bone in the anatomical position and note the following:
  • The anterior border is concave forwards and Subclavius shows a small rough area called a deltoid tubercle.
  • The posterior border is rough and convex posteriorly.
  • The superior surface is mostly smooth except near its anterior and posterior borders, which give attachment to muscles. Now turn the bone upside down to see the inferior surface of lateral1/3.
  • The inferior surface near its posterior border shows a tubercle known as conoid tubercle.
  • A thick ridge extends forward and laterally from the conoid tubercle. This ridge is known as the trapezoid ride.

The lateral end of the bone bears a small oval facet for articulation with the acromian process of the scapula to form an acromioclavicular joint.

Upper Limb Bones

Particular Features Muscles Attached to Bone

Draw the attachments of muscles on the surface of the bone with the help of colored chalk.

Bones Of The Upper Limb Attachment Of Muscles On Inferrior Surface

Bones Of The Upper Limb Attachment of muscles on inferior surface.

Medial 2/3 of Clavicle

  • The superior surface is covered by skin and platysma muscle. The clavicular head of the sternocleidomastoid muscle arises from the medial third of this surface.
  • The anterior surface of the medial half of the clavicle gives origin to the clavicular head of pectoralis major.
  • The muscle sternohyoid is attached near the medial end of the posterior surface of the clavicle.
  • On the inferior surface, the subclavius muscle is attached to the subclavian groove.
  • The margins of this groove give attachment to clavipectoral fascia.

Bones Of The Upper Limb Inferior Surface Showing Attachment of Ligaments

Lateral 1/3 of the Clavicle

  • The anterior border gives origin to the deltoid muscle.
  • The posterior border gives attachment to the trapezius muscle.
  • Costoclavicular ligament
  • Ligaments Attached to Bone
  • The attachments of the articular capsule at its medial and lateral ends are shown in.
  • The costoclavicular ligament is attached to the inferior rough surface near its medial end.

Bones Of The Upper Limb Costoclavicular Ligament

  • The interclavicular ligament and the articular disc of the sternoclavicular joint are attached to the medial surface of the medial end.
  • Conoid and trapezoid parts of the coracoclavicular ligament are attached on the conoid tubercle and trapezoid ridge respectively on the inferior surface of lateral 1/3.

Upper Limb Bones

Nerves and Blood Vessels Related To Bone

  • Three supra-clavicular nerves (medial, intermediate, and lateral) are related to its anterosuperior surface.

Bones Of The Upper Limb Superior View Of Left Clavicle

Bones Of The Upper Limb Inferior veiw of clavicle

Bones Of The Upper Limb Lateral aspect of the left scapula

  • There lasted posterior to the surface trunks of medial brachial 2/3 of the plexus, shaft in the third part of subclavian vessels, and internal jugular vein.

Clavicle Fracture

Peculiarities of the Clavicle

  • Though it is a long bone but is placed horizontally.
  • Though long bone but ossifies mostly from membrane.
  • It is devoid of a medullary cavity.
  • The first bone to start ossifying in the body.

Clavicle Clinical Application

The main function of the clavicle is to transmit the forces from the upper limb to the axial skeleton through the sternoclavicular joint.

The forces are transmitted from the humerus to the scapula and then from the scapula to the clavicle through the coracoclavicular ligament. If the force, during a fall on the outstretched hand, is greater than the strength of the clavicle, a fracture will result at the junction between two curvatures of bone (medial 2/3 and lateral 1/3).

After the fracture, the shoulder drops, and the lateral fragment of the clavicle is displaced downward due to the weight of the upper limb (gravity).

Clavicle Fracture

The medial fragment of bone is pulled upward due to the action of the clavicular head of the sternocleidomastoid muscle.

The lateral fragment of the bone may also be pulled medially by the action of the pectoralis major.

Thus two fragments may override each other. To approximate the two fractured ends of the bone, a bandage in the shape of a figure of eight is tied.

The clavicle acts as a strut to keep the shoulder laterally. This helps the upper limb to swing away from the trunk.

In a congenital malformation known as cleidocranial dysostosis, the clavicle is either absent or imperfectly developed.

In this condition shoulder joint is not always placed laterally and can be brought in front of the chest.

Bones Of The Upper Limb Peculiarties Of The Clavicle

  • The concave posterior surface of medial 2/3 of the bone protects the nerves and vessels (trunks of brachial plexus and subclavian vessels), which go from the root of the neck to the axilla.

Clavicle Fracture

Bones Of The Upper Limb Fracture Of Clavivle. Note The over-Riding of two Fragments Of The bone

Clavicle Ossification

The clavicle is the first long lone to ossify in the embryo. It is organized by two primary centers and one secondary center. Most of the shaft ossifies by membranous ossification.

Bones Of The Upper Limb Ossification Of Bone

The Scapula or Scapula Bone

The description of the scapula is in the following two paragraphs and a reference will help you learn to determine its side and to keep it in the anatomical position. The scapula is also known as the “shoulder blade”.

It is the posterior bone of the shoulder girdle. It lies on the posterolateral aspect of the thorax extending between the 2nd and 7th rib.

The body- of the scapula is thin, flat, and triangular.

Upper Limb Bones

Bones Of The Upper Limb Anterior (costal) surface surface of the right scapala

As the body is triangular it has three borders (medial, lateral, and superior) and three angles (superior, lateral, and inferior).

The inferior angle is directed downwards and lies at the level of the 7th rib. Just opposite the inferior angle is a superior border that extends between superior and lateral angles.

Scapula Bone

At the lateral angle, there is the presence of a shallow smooth articular fossa called a glenoid cavity, which articulates with the head of the humerus to form a shoulder joint.

The medial border runs between superior and inferior angles and is quite thin. The lateral border is thick and runs between lateral and inferior angles.

Bones Of The Upper Limb Posterior Surface Of the Right Scapula

The scapula shows two surfaces, i.e., costal and dorsal. The costal (anterior) surface is smooth and forms a shallow fossa called as subscapular fossa.

On the other hand dorsal (posterior) surface is convex posteriorly and is divided into supraspinous and infraspinous fossae by the presence of a bony process called as spine of the scapula.

Scapula Bone

It is a thick projecting ridge of bone, which is continuous laterally as the flat expanded acromion process. A beak-like bony process (coracoid process) arises from the upper part of the glenoid cavity.

Scapula Side Determination

Scapula Hold the bone in such a way that:

  • The inferior angle is directed downwards and the superior border is directed upwards.
  • The costal or anterior surface should face anteriorly and the dorsal (posterior) surface, bearing the spinous process, should face posteriorly.
  • The glenoid cavity should face laterally.

Bones Of The Upper Limb Lateteral Aspect Aspect Of Lelt Scapula

  • In this position, the direction of a glenoid cavity will determine the side of the bone.

Scapula Anatomical Position

  • Hold the bone in such a way that the coastal surface should face antero-medially.
  • The glenoid cavity should face anterolaterally and slightly upwards.

Scapula General Features

We shall study the general features of the scapula under four different headings, i.e., surfaces, borders, angles, and processes.

Surfaces

Costal (anterior) surface: The costal surface is slightly concave and forms a large subscapular fossa. There is the presence of a bar of thickened bone near the lateral border extending. between the head of scapula (lateral angle) and the inferior angle.

Dorsal (posterior) surface: The spine of the scapula divides the dorsal surface into a smaller upper supraspinous fossa and a larger infraspinous fossa. Both these fossae are continuous with each other through spinoglenoid notch.

Borders

Medial border: The medial border of the scapula is thin and lies about 5 cm lateral to the spinous processes of the thoracic vertebrae.

Lateral border: This border extends from the lowest part of the glenoid cavity to the inferior angle.

It is a sharp ridge. Close to the lateral border, on the costal surface, there is the presence of a thickened longitudinal bar of the bone. It should not be confused with the lateral border.

Superior border: It extends between the superior angle and the root of the coracoid process. This border presents a suprascapular notch close to the root of the coracoid process.

Angles

The superior and inferior angles of the scapula are present at the upper and lower ends of the medial border respectively.

The lateral angle of the scapula is the thickest part of the bone where the glenoid cavity is present. This broadened part of the bone is sometimes called as head of the scapula. A constriction between the head and body is called as neck of the scapula.

The glenoid cavity is a shallow, concave, oval fossa. There is a presence of rough areas just above and below the glenoid cavity. These are called supraglenoid and infraglenoid tubercles respectively.

Scapula Processes

The spine of the scapula is a triangular bony process present on the dorsal aspect of the body. Its anterior border is attached to the dorsal surface of the body while its posterior border is free.

This thick posterior border of the spine is also known as the crest of the spine. The lateral border of the spine forms the boundary of the spinoglenoid notch.

The acromion process is a forward projection from the lateral end of the spine. It is a flat, expanded, subcutaneous process, which overhangs the glenoid cavity.

It has medial and lateral borders and superior and inferior surfaces. It articulates with the lateral end of the clavicle to form an acromioclavicular joint. The coracoid process is so named because it resembles the beak of a crow.

It is present superior to the glenoid cavity and is shaped like a bent finger. In the anatomical position, it projects anterolaterally.

Scapula Particular Features

Muscles Attached to Bone

Draw the attachments of muscles on the surface of the bone with the help of colored chalk as shown in

  • Almost the whole of the costal (anterior) surface (except a small part near the neck) gives origin to the subscapularis muscle.
  • The medial border on the costal surface gives attachment to the serratus anterior.

Bones Of The Upper Limb Attachment Of Muscles On Dorsal Surface

Bones Of The Upper Limb Attachment Of Muscles On Costal Surface

  • The inferior belly of the omohyoid is attached to the superior border near the suprascapular notch.
  • On the dorsal surface, the supraspinous fossa gives origin to the supraspinatus muscle and infraspinous fossa to the infraspinatus respectively.
  • The teres major and teres minor arise from the dorsal surface close to the lateral border.
  • Attachments of levator scapulae, rhomboideus minor, and rhomboideus major on the dorsal surface of the medial border.
  • The supraglenoid tubercle gives origin to the long head of biceps brachii.
  • The long head of the triceps arises from the infraglenoid tubercle.
  • The coracobrachialis and short head of biceps arise from the tip of coracoid process.
  • Pectoralis minor is inserted on the superior aspect of the coracoid process.
  • The deltoid muscle arises from the lower border of the crest of the spine and the lateral border of the acromion process.
  • The medial border of the acromion and upper border of the crest of the spine gives insertion to the trapezium.

Ligaments Attached to Bone

  • The attachments of the capsule of the shoulder joint and acromioclavicular joints.
  • The suprascapular ligament is attached to the superior border above the suprascapular notch
  • Three ligaments are attached to the coracoid process, i.e., coracohumeral, coracoacromial, and coracoclavicular.
  • One end of the coracoacromial ligament is attached to the lateral border of the coracoid process and the other end is to the tip of the acromian process. The coracohumeral is attached to the root of the coracoid process.
  • The conoid part of the coracoclavicular ligament is attached near the root, while the trapezoid part is on the superior aspect of the coracoid process.

Bones Of The Upper Limb Attachments Of Ligamnets

Bones Of The Upper Limb Attachments Of Ligaments.

Nerves and Blood Vessels Related to the Bone

The suprascapular vessels lie above the suprascapular ligament, while the suprascapular nerve passes deep to it These vessels and nerves then lie in These vessels and nerve then lie in spinoglenoid notch.

Bones Of The Upper Limb Nerve and Blood Vessels Related To Scapula

  • The circumflex scapular branch of the subscapular artery comes in contact with the lateral border on its dorsal aspect between two heads of teres minor.
  • The dorsal scapular nerve and vessels lie close to the medial border.

Scapula Ossification

The scapula ossifies by one primary and 7 secondary centers (2 for the coracoid process, 2 for acromion, 1 each for the glenoid cavity, inferior angle, and medial border).

The lower center of the coracoid process fuses with the body by the 16th year while other centers by the end of the 20th year.

Bones Of The Upper Limb Ossification Of Scapula

Humerus

The humerus is the longest bone of the upper limb. It has two ends and a shaft. The proximal (upper) end shows a large, smooth, rounded head that articulates with the glenoid cavity of the scapula to form the shoulder joint. The head is directed medially.

There is the presence of a deep vertical groove {inter-tubercular sulcus or bicipital groove) on the anterior aspect of the upper end.

The middle part of the shaft is almost cylindrical. The lower end is expanded from side to side and flattened from before backward. It has two articular structures, i.e., a rounded capitulum and the pulley-shaped trochlea.

On the posterior aspect of the lower end, there is a large olecranon fossa just above the trochlea. The medial and lateral epicondyles are bony non-articular projections at the lower end.

Humerus Side Determination

  • You should keep the bone vertical in such a way that the head faces medially.

Bones Of The Upper Limb Posterior Aspect Of Right Humerus

Bones Of The Upper Limb Posterior Surface Of Right Radius

  • The intertubercular sulcus on the anterior aspect of the upper end should face anteriorly.
  • The olecranon fossa, at the lower end, should face posteriorly

Humerus Anatomical Position

Hold the bone vertically in such a way that the head faces medially and slightly upwards and backward.

Humerus General Features

We shall study the general features of bone under three headings, i.e., upper end, shaft, and lower end

Humerus Upper end

The upper end consists of the head, neck, greater and lesser tubercles, and an intertubercular sulcus (bicipital groove).

Bones Of The Upper Limb Ventral Aspect Of The Left Scapula

Bones Of The Upper Limb Anterior Aspext Of Upeer End Of Left Humerus

Bones Of The Upper Limb Anterior Aspect Of The Lower End Of Left Humerus

  • The head has a convex, rounded, and smooth articular surface.
  • The junction of the articular head with the rest of the upper end is called as anatomical neck.
  • The junction of the upper expanded end with the shaft is called a surgical neck.
  • The lesser tubercle is present on the anterior aspect of the upper end while greater tubercle is present on its anterolateral aspect.
  • There is the presence of an intertubercular sulcus between these two tubercles.
  • Both the tubercles on their upper surface show the presence of smooth areas for the attachment of muscles.

Humerus Shaft

The shaft is almost cylindrical in the upper half and triangular in the lower half. It presents three borders and three surfaces.

Borders

  • Trace the lateral lip of the bicipital groove downward. You will see that it becomes continuous with the anterior border of the shaft.
  • The medial border of the bicipital groove is continuous downwards as the medial border.
  • If this border is further traced downwards it becomes continuous as medial supracondylar ridge.

Bones Of The Upper Limb Features On Superior Surface Or Upeer End Of Right Humerus

  • The lateral border of the shaft is well-defined only in the lower part of the shaft where it becomes continuous with the lateral supracondylar ridge.

Humerus Surfaces

  • The anteromedial surface is between the anterior and medial border.
  • The anterolateral surface is between anterior and lateral borders. Just above the middle of the bone, this surface shows a V-shaped rough area called deltoid tuberosity.
  • The posterior surface is situated between lateral and medial borders. In its middle 1/3, it shows the presence of a shallow groove (radial groove) running downwards and laterally.

Humerus Lower End

  • The lower end shows the presence of a rounded articular area known as the capitulum. It is placed laterally and articulates with the upper end of the radius.
  • The pulley-like trochlea is placed medially and articulates with the trochlear notch of the ulna.
  • There is a presence of shallow fossa above the capitulum (known as radial fossa) and coronoid fossa just above the trochlea. When the forearm is flexed, the coronoid fossa and radial fossa receive the coronoid process and head of radius respectively.
  • The olecranon fossa is quite large and situated on the posterior surface of the lower end just above the trochlea. It receives the olecranon of the ulna when the forearm is extended.
  • If you will trace the medial and lateral supracondylar ridges downwards, you will reach the bony projections on either side of the lower end.
  • These rough projections are known as epicondyles. The medial epicondyle is the prominent subcutaneous projection, which you should palpate (feel) in your limb.

Bones Of The Upper Limb The Lower End Of Right Humerus As Seen From Inferior Aspect

Humerus Particular Features

Muscles Attached to Bone

Upper End

  • The three impressions on the surface of the greater tubercle give insertion to supraspinatus, infraspinatus, and teres minor.
  • The subscapularis muscle is inserted on the lesser tubercle.
  • The tendon of the long head of the biceps passes through the bicipital groove.

Bones Of The Upper Limb Attachment Of Muscleus On Posterior Aspect Of Right Humerus

Bones Of The Upper Limb Attachment Of Muscles On The Anterior Aspect Of Right Humerus

Shaft

Shaft Anterior Aspect

  • On the anterior aspect of the shaft, the medial lip of the bicipital groove gives attachment to the teres major while the lateral lip to the pectoralis major.
  • The floor of the bicipital groove gives insertion to the latissimus dorsi.
  • On the V-shaped deltoid tuberosity deltoids are attached.
  • The coracobrachialis is attached to the middle of the medial border.
  • The brachialis muscle arises from the front aspect of the lower half of the shaft.
  • The pronator teres take origin from the medial supracondylar ridge.
  • The lateral supracondylar ridge gives origin to the brachioradialis and extensor carpi radialis longus.

Shaft Posterior Aspect

  • The lateral head of the triceps arises above the radial groove.
  • Below the radial groove, the posterior surface gives origin to the medial head of the triceps.

Shaft Lower End

  • The front of the medial epicondyle gives origin to the superficial flexor muscles of the forearm. This origin is known as “common flexor origin”.
  • The anterior aspect of the lateral epicondyle gives origin to extensors of the forearm hence known as “common extensor origin”.
  • The anconeus originates from the posterior surface of the lateral epicondyle.

Ligaments Attached to Bone

  • The attachments of the articular capsule for shoulder joint and elbow joints.
  • The ulnar collateral ligament of the elbow joint is attached to the medial epicondyle.
  • The radial collateral ligament is attached to the lateral epicondyle.

Nerves and Vessels Related to the Bone

The surgical neck of the humerus is related to the anterior and posterior circumflex humeral vessels and the axillary nerve.

Bones Of The Upper Limb Nerves And Vessels Related To Humerus

  • The radial nerve and profunda/brachial vessels are related to the radial groove.
  • The ulnar nerve lies just posterior to the medial epicondyle.

Shaft Clinical Importance

  • The common sites of fracture are the surgical neck, middle of the shaft, and supracondylar region.
  • The fracture of the surgical neck of the humerus is common in old people. The axillary nerve, which is in direct contact with the neck, may get injured.
  • The supracondylar fractures are common in young individuals. The median nerve and brachial artery may get injured as they are related to the lower end.
  • The fracture of the middle of the shaft may be due to a direct blow to the arm. Here the radial nerve in the radial groove may get injured.
  • The avulsion fractures of the greater tubercle of the humerus are also common (in this fracture the greater tubercle is pulled away from the rest of the upper end). This may result in to fall on the hand while the arm is abducted.
  • The fracture of the medial epicondyle is usually associated with the injury of ulnar nerve, as it lies just posterior to the epicondyle.
  • As the upper end of the humerus is the growing end, the bone keeps on growing in a young individual even after the amputation of an arm.
  • Hence, at the time of amputation of the arm care should be taken that sufficient soft tissue should be left distal to the site of amputation so the bony stump will not penetrate soft tissues.

Shaft Ossification

The upper end ossifies by 3 and the lower end by 4 secondary centers Upper end is the growing end as the secondary center appears first and fuses last (at 20 years).

Bones Of The Upper Limb Ossification Of humerus

Radius

  • The radius is situated on the lateral side (thumb side) of the forearm. Like any other long bone, it also consists of the upper end, shaft, and lower end.
  • The upper (proximal) end of the radius is narrow while its lower end is wide. The upper end presents a disc-shaped head, a neck, and medially directed radial tuberosity.
  • The shaft of the radius has a laterally directed convexity. The medial border is sharp and called an interosseous border. The lower end is wide and shows anterior, posterior, medial, and lateral surfaces.
  • The posterior surface of the lower end is rough and presents a dorsal tubercle. A projection (styloid process) is present on the lateral aspect of the lower end.

Radius Side Determination

  • Keep the bone vertically in such a way that the narrow disc-shaped upper end is directed upward (proximally).
  • At the expanded lower end, the dorsal tubercle should face backward and styloid process directed laterally and downwards.
  • In this position, a sharp border of the shaft (interosseous border) should be directed medially.

Bones Of The Upper Limb Anterior Surface Of Right Radius

Radius Anatomical Position

Hold the bone vertically in such a way that the head is directed upwards, with radial tuberosity and sharp border medially, and dorsal tubercle posteriorly.

Bones Of The Upper Limb Posterior Surface Of Right Radius

General Features Upper End

The upper end consists of the head, neck, and radial tuberosity.

  • The disc-shaped head shows an upper surface, which is slightly concave to articulate with the capitulum of the humerus.
  • The circumference of the head articulates medially with the radial notch of the ulna to form the superior radioulnar joint. The rest of the circumference of the head is surrounded by an annular ligament.
  • The constriction just below the head is known as the neck.
  • There is a prominent elevation just below the medial part of the neck. This is known as radial tuberosity.

Shaft

  • The shaft shows 3 borders and three surfaces.
  • Trace the anterior border from the anterior aspect of radial tuberosity to the styloid process.
  • Trace the posterior border from the posterior Upper-End aspect of the radial tuberosity to the posterior aspect of the lower end Trace the sharp medial (interosseous) border from the lower aspect of radial tuberosity to the posterior margin of the ulnar notch.
  • The anterior surface lies between anterior and medial borders while the posterior surface lies between posterior and medial borders.
  • The lateral surface is present between anterior and posterior borders. This surface is convex laterally and shows a rough area near the middle part of the shaft.

Lower End

  • The lower end is the expanded end and shows anterior, posterior, lateral, and medial surfaces.
  • It also shows an inferior surface, which is smooth (articular) and articulates with the scaphoid laterally and lunate bone medially to form the wrist joint
  • The lateral surface when traced downwards, projects as a styloid process.
  • The medial surface shows an ulnar notch. It articulates with the head of the ulna to form an inferior radioulnar joint.

Bones Of The Upper Limb The Inferior Surface Of Radius And Ulna Of Right Side

Radius Particular Features

Muscles Attached to the Radius

Upper End

The biceps brachii is inserted on the rough posterior part of the radial tuberosity. The anterior smooth part of the radial tuberosity is in relation with the bursa.

Shaft and Lower End

  • The upper part of the anterior border gives origin to the radial head of flexor digitorum superficialis.
  • The upper of the anterior surface gives origin to the flexor pollicis longus.
  • The pronator quadratus is inserted into the lowermost part of the anterior surface. The attachment also extends on the medial surface of the lower end. posterior surfaces give insertion to the supinator.
  • The rough area on the middle of the lateral surface gives insertion to pronator teres.
  • The muscle brachioradialis is inserted into the lowest part of the lateral surface just above the styloid process.
  • The abductor pollicis longus and extensor pollicis brevis arise from the posterior surface of the shaft.

Bones Of The Upper Limb Attachment Of Muscles On The Anterior Aspects Of The Radius

Ligaments Attached to the Bone

  • Note the attachment of the articular capsule of the wrist joint on the lower end of the radius.
  • The interosseous membrane is attached to the lower 3A of the medial border.
  • The articular disc of the inferior radioulnar joint is attached to the lower border of the ulnar notch.
  • The anterior border near the lower end gives attachment to the extensor retinaculum.
  • The radial collateral ligament of the wrist joint is attached to the tip of the styloid process.

Tendons and Arteries with the Bone

  • The relationship of tendons on the dorsal aspect of the lower end
  • The radial artery is related to the anterior surface of the lower end. Here the pulsations of the artery can be easily felt by applying pressure against the radial bone.

Bones Of The Upper Limb Attachment Of Ligaments And Relation Of Radial Artery On Ventral Aspect

Bones Of The Upper Limb Tendons Related To Dosaral Of Lower End

Radius Clinical Importance

Though the fracture of the radius may occur at its upper end and shaft the fracture of the distal end of the radius is most common, especially in old women.

A fracture of the lower end of the radius is called a Colies’s fracture. The fracture usually results from a fall on an outstretched hand.

The distal fragment overrides and is displaced dorsally. This results in a shortening of radius.

As a result the styloid process of both the bones (radius and ulna) now lies almost at the same level. The clinical deformity is often referred to as “dinner fork deformity.

Bones Of The Upper Limb Colles's fracture

Radius Ossification

Radius ossifies by one primary and two secondary centers, i.e., one for each end. The lower end is the growing end.

Ulna

  • The ulna is the medial bone of the forearm. It is longer than the radius. The ulna has an upper end, a lower end, and a shaft. The upper end of the ulna is expanded, and irregular and presents a deep notch, which faces anteriorly.
  • This notch is called a trochlear notch and it articulates with the trochlea of the humerus at the elbow joint. While its lower end is small and has a tiny styloid process.
  • You should remember that the lower end of the ulna is called as head. The shaft has a sharp lateral margin.
  • This margin gives attachment to the broad, flat, fibrous connective tissue called interosseous membrane. The ulna is connected with the radius by an interosseous membrane.

Ulna Side Determination

  • Hold the bone vertically in such a way that its expanded hook-like end is directed upwards and the small rounded lower end is directed downwards.
  • The concavity of the trochlear notch (at the upper end) should face anteriorly.
  • The sharp border of the shaft should be directed laterally.

Ulna Anatomical Position

Hold the bone vertically in such a way that the trochlear notch faces anteriorly, the sharp border of the shaft laterally, and the styloid process at the lower end is present posteriorly.

Bones Of The Upper Limb Anterior Aspect Of The Right Ulna

Ulna General Features

Ulna Upper End

The upper end of the ulna presents the olecranon process, coronoid processes, and two articular surfaces, i.e., trochlear and radial notches.

Olecranon Process

  • The olecranon process is the uppermost part of the ulna. It has superior, anterior, posterior, medial, and lateral surfaces.

Bones Of The Upper Limb Posterior Aspect Of Right Ulna

Bones Of The Upper Limb The Upper End Of Right Ulna Showing Olecranon And Coronoid Processes

Bones Of The Upper Limb Upper End Of Left Radius ant view

Bones Of The Upper Limb Posterior View, Lower End Radius

Bones Of The Upper Limb Ulna Upper End, Lateral Surface

Bones Of The Upper Limb Ulna Upper End, Medial Surface

  • The anterior surface of the olecranon process forms the upper part of the trochlear notch.
  • The posterior surface of this process is triangular and smooth because it lies just beneath the skin.

Coronoid Process

  • The coronoid process projects anteriorly from the shaft just below the olecranon.
  • It has four surfaces, i.e., superior, anterior, medial, and lateral.
  • The superior (upper) surface is almost horizontal and forms the lower part of the trochlear notch.
  • The anterior surface is triangular and is rough in its lower part. The rough area is known as the tuberosity of the ulna.

Radial Notch

The lateral surface of the coronoid process has a concave articular area. This is known as a radial notch. It articulates with the head of radius forming the superior radioulnar joint.

Trochlear Notch

  • It articulates with the trochlea of the humerus. It is formed by the anterior surface of the olecranon and the upper surface of the coronoid process. There may be a non-articular area(groove) between the two parts.

Lower End

  • The lower end (head) is small and rounded.
  • Anteriorly and laterally it articulates with the ulnar notch of the radius to form an inferior radioulnar joint.
  • The inferior surface is separated from the cavity of the wrist joint by an articular disc.
  • The styloid process projects downwards from the posteromedial aspect of the lower end.

Shaft

  • The cross-section of the shaft is almost triangular.
  • It presents anterior, lateral, and posterior borders and anterior, medial, and posterior surfaces.
  • The lateral or interosseous border is sharp. When traced upwards, it becomes continuous with a rough ridge present just posterior to the radial notch. This rough ridge is known as the supinator crest.
  • The anterior and posterior borders are rounded. The anterior border begins at the lower end of the tuberosity of the ulna and ends on the anterior aspect of the styloid process.
  • The anterior surface lies between the anterior and interosseous border and shows the presence of an oblique ridge in its lower part.
  • The posterior surface lies between inter osseous and posterior border. The posterior surface is subdivided into medial and lateral parts by a vertical ridge.

Ulna Particular Features

Muscles Attached to Bone

Upper End

  • The triceps is inserted on the posterior part of the upper surface of the olecranon process.
  • Brachialis is attached to the anterior surface of the coronoid process and the tuberosity of the ulna.
  • The supinator arises from the supinator crest and a triangular area just below the radial notch.

Bones Of The Upper Limb Attachment Of Muscles On The Anterior SUrface Of Right Ulna

Bones Of The Upper Limb Attachment Of muscles On The Posterior Surface Of Left Ulna

  • The medial border of the coronoid process gives origin to the ulnar head of flexor digitorum superficialis above and pronator teres below.
  • The anconeus is inserted into the lateral aspect of the olecranon and the upper part of the posterior surface of the shaft.
  • The ulnar head of the pronator teres arises from the medial margin of the coronoid process.
  • The ulnar head of the flexor carpi ulnaris arises from the medial side of the olecranon process and from the upper two-thirds of the posterior border through aponeurosis.
  • From the same aponeurosis, ulnar head of extensor carpi ulnaris also arise.

Shaft

  • Flexor digitorum profundus takes origin from the anterior and medial surface of the shaft On the anterior surface the oblique ridge gives origin to the pronator quadratus
  • Three muscles are attached on the posterior surface (between the interosseous border and a vertical ridge) from above downwards i.e., abductor pollicis longus, extensor pollicis long, and extent or indices.

Ligaments Attached to Bone

  • The capsular ligament of the elbow joint is attached to the margins of the coronoid and olecranon process.

Bones Of The Upper Limb Attachment Of Interosseous membrane Transerve Section Through Radius And Ulna

  • The capsular ligament of the inferior radioulnar joint is attached close to the articular area.
  • The apex of the triangular articular disc is attached to the lateral aspect of the styloid process.
  • The interosseous membrane is attached to the sharp interosseous border.
  • The annular ligament of a superior radioulnar joint is attached to the anterior and posterior border of the radial notch.
  • The oblique cord is attached to the lateral aspect of the ulnar tuberosity.
  • The ulnar collateral ligament of the wrist joint is attached to the tip of the styloid process.

Ulna Clinical Importance

  • Though the fractures of both the radius and ulna may result due to severe injury isolated fractures of the radius and ulna may also occur.
  • The most common fracture of the ulna along with the radius is through the middle of the shaft or at its lower end. Sometimes a fracture of the olecranon can occur due to a fall on the elbow.

Ulna Ossification

Ulna ossifies by 3 centers, i.e., one primary and two secondary, i.e., one each for upper and lower end. The lower end is the growing end.

Bones Of The Hand

The bones of the hand consist of carpals, metacarpals, and phalanges.

Carpal Bones

The skeleton of the wrist consists of eight small bones, which are arranged in two transverse rows of four bones each. These bones are called carpal banks. They are named as per their shapes.

The proximal row, from lateral to medial side, consists of:

Bones Of The Upper Limb Ossification Of Ulna

Bones Of The Upper Limb Bones Of The Right Hand

Bones Of The Upper Limb Schematic Diagram Of Left Carpal Bones As Seen From Anterior Aspect

  • Lunate (It is moon-shaped).
  • Triquetrum (It has three corners and is pyramidal). Pisiform (It is pea shaped small bone that lies on the anterior surface of the triquetrum).
  • The carpal bones in the distal row, from lateral to medial, are:
  • Trapezium (table-shaped, four-sided).
  • Trapezoid (wedge-shaped).
  • Capitate (It is cap-shaped and has a rounded head).
  • Hamate (It has a hook-shaped process).

Joints Formed by the Carpal Bones

  • The wrist joint is formed between the proximal surfaces of three carpal bones of the proximal row and the lower end of the radius.
  • The scaphoid and lunate of the proximal row articulate with the inferior articular surface of the radius, while the triquetrum is related to the articular disc and thus separated from the head of the ulna.
  • Carpal bones are joined to one another by interosseous ligaments and intercarpal joints.
  • The distal articular surfaces of the carpal bones of the distal row articulate with the metacarpals to form carpometacarpal joints.

Bones of the Hand Clinical importance

  • The common injury of the wrist consists of fracture of the scaphoid or lunate.
  • The fracture of the scaphoid is the most common. It results in a fall on an outstretched hand. In this condition, the line of fracture passes almost from the middle of the bone dividing the bone into proximal and distal fragments. The patient complains of pain in the scaphoid fossa (lateral side of the wrist.
  • As the nutrient arteries scaphoid enter the distal end of the bone, the proximal segment is devoid of the blood supply after fracture. This may result in avascular necrosis (death due to inadequate blood supply) of the proximal fragment of the scaphoid.
  • Thus scaphoid fracture heals poorly, i.e., may take several months to heal.
  • The fracture of hamate also heals poorly due to the traction produced by the attached muscles.
  • As the ulnar nerve lies close to the hook of hamate, it may also get injured due to the fracture of the hamate.

Metacarpals

Metacarpals are miniature long bones, which form the skeleton of the palm. They are five in number and are numbered from the lateral to the medial side. The metacarpal of the thumb is known as the first metacarpal while that of the little finger is known as the fifth (V) metacarpal.

Each metacarpal bone consists of a proximal base, an intermediate shaft, and a distal head.

Bones Of The Upper Limb General Features Of A Metacarpal Bone

Bones Of The Upper Lower End Of Left Ulna As Seen From Behind

Bones Of The Upper Limb Ventral Aspect Of Left Carpal Bones And Base Of Metacarpals

  • The proximal ends or bases of the metacarpal are irregularly expanded and articulate with the carpal bones. The distal ends (heads) are rounded and articulate with the proximal phalanges.
  • The shaft of each metacarpal is curved with the concavity looking forward. It has three surfaces, i.e., medial, lateral, and posterior.
  • The first metacarpal is easily distinguished from the rest because it is the thickest and shortest of all the metacarpals. The articular surface at its base is concavoconvex which articulates with trapezium.
  • The third metacarpal can also be differentiated from the rest because it has a styloid process on the lateral side of its base.

Joints Formed by the Metacarpals

  • The distal articular surfaces of the carpal bones of the distal row articulate with the metacarpals to form carpometacarpal joints.
  • The trapezium articulates with the first metacarpal, the trapezoid with the second, the capitate with the third, and the hamate with the fourth and fifth metacarpals.
  • The distal articular surfaces of metacarpals articulate with the proximal articular surfaces of proximal phalanges to form carpometacarpal joints.

Phalanges

  • Phalanges are the bones of digits. Each digit has three phalanges (i.e., proximal, middle Flexor carpi, and distal) except the first (for thumb), which has only two phalanges.
  • Each phalanx has a proximal base, a body, and a distal head. The proximal phalanges are the longest and most articulate with the head of metacarpals at their bases to form metacarpophalangeal joints.
  • The middle phalanges are intermediate in size and articulate at their bases with the heads of proximal phalanges to form proximal interphalangeal joints.
  • The distal phalanges are smallest, flattened, and expanded at their distal ends (non-articular) to form the nail beds.

Particular Features of the Bones of Hand

  • Insertion of forearm muscles on the palmar surface of the hand.
  • The flexor carpi ulnaris is attached on the pisiform bone. From this bone abductor digiti minimi also takes origin.

Bones Of The Upper Limb Attachment(Insertion) Of Forearm Muscles On the Palmar Surface Of Right Hand

  • Flexor carpi radialis is inserted on the base of the 2nd and 3rd metacarpals on their palmar surface.
  • The flexor digitorum profundus is inserted on the bases of distal phalanges, while flexor digitorum superficialis is inserted on both the sides of middle phalanges of all the fingers except that of the thumb.
  • The flexor pollicis longus is inserted on the base of the distal phalanx of the thumb, on its palmar surface.

Insertion of forearm muscles on the dorsal aspect of the hand and dorsal interossei.

  • The extensor carpi ulnaris is attached to the base of the fifth metacarpal; the abductor pollicis longus to the base of the first; the extensor carpi radialis longus to the base of the second; extensor carpi radialis brevis to the bases of 2nd and 3rd metacarpal.

Attachments of Ligaments

  • The attachment of carpal bones with each other (due to their shape) presents a concavity forward.
  • The attachment of the flexor retinaculum medially to the hook of the hamate and pisiform bone and laterally to the tubercles of the scaphoid and trapezium
    form an osteofascial carpal tunnel.
  • Through this tunnel passes the tendons, vessels, and nerves from the forearm to the hand.
  • Pisiform bone gives attachment to two ligaments, i.e., first extending from pisiform to the base of the fifth metacarpal (pisometacarpal) and second from pisiform to the hook of the hamate (pisohamate).
  • The medial end of the extensor retinaculum is attached to the triquetral and pisiform bones.
  • The lateral margins of each phalanx give attachment to the fibrous flexor sheath.

Bones Of The Upper Limb Attachment Of Muscles On The Dorsal Surface Of Right Rand

Bones Of The Upper Limb Attachment Of Muscles On Palmar Surface Of Right Hand

Bones Of The Upper Limb Attachment of pisometacarpal and Pisohamate Ligaments

Bones Of The Head And Neck Regions Notes

Bones Of The Head And Neck Regions

  • The bones of the head and neck regions consist of the skull, cervical vertebrae, and hyoid bone.
  • The skull forms the skeleton of the head region. the skull contains a large cavity for the lodgment of the brain (called a cranial cavity) and two small cavities for the lodgment of the eyes (called orbits).
  • On the anterior aspect of the skull, there are two openings, i.e., the opening of nasal cavity and the opening of the oral cavity (mouth).
  • Below the skull, the skeleton of the neck is formed by the seven cervical vertebrae.
  • The hyoid bone is a small bone, present in the upper part of the neck in front of the 3rd cervical vertebra.

Anterior Nasal Aperture

Skull

The skull (the skeleton of the head) is formed by 22 bones. These bones are firmly joined to one another and are immobile except for the bone of the lower jaw (mandible), which moves at the temporomandibular joint. The skull is divided into two parts, i.e., cranium and facial skeleton.

Cranium

  • It is also known as the neuro-cranium, brain box, or calvaria. The cranium is the upper and posterior part of the skull.
  • Cranium means skull minus the mandible.
  • It consists of 8 bones. Out of these 8 bones, 4 are unpaired (frontal, occipital, sphenoid mid ethmoid) and 2 are paired (parietal and temporal).
  • The joints between these bones are immobile and are known as sutures.
  • The cranium has a dome-like roof (called a vault or skull cap) and a floor or cranial base (called basi-cranium.

Anterior Nasal Aperture

Bones Of The Head And Neck Regions Skull As Seen In Lateral View

Facial Skeleton (Viscerocranium)

  • The facial skeleton forms the anterior part of the skull. It contains orbital and nasal cavities and includes upper and lower jaws (maxillae and mandible).
  • In addition to the frontal bone, the facial skeleton consists of 14 bones. Out of these 6 are paired (lacrimal, nasal, maxillae, zygomatic, palatine, and inferior nasal conchae). While the mandible and vomer are single bones.

Read and Learn More Human Osteology Notes

Anatomical Position of the Skull

To obtain the anatomical position of the skull, it is kept in the “Frankfurt horizontal plane”.

  • Hold the skull in such a way that the inferior border of the orbit and the superior border of the external acoustic meatus of the right and left sides lie in the same horizontal plane.
  • Students are suggested to identify various bones of a dry skull with the help. Once they can identify various bones in the skull then only they should proceed to study the details of the skull as seen from various aspects.

Anterior Nasal Aperture

Bones Of The Head And Neck Regions Sagittal Section Of The Skull Showing Cranial And Nasal Cavities

Bones Of The Head And Neck Regions Skull As Seen From Anterior Aspect

A dry skull may be viewed from:

  • Above (norma verticalis,.
  • Behind (norma occipitalis,
  • Front (norma frontalis). The walls of the orbital cavity can also be examined from this view.
  • And from the side (norma lateralis,.
  • Below (norma basalis externa,
  • The roof of the calvaria (skull cap) may be removed by a transverse cut to examine the inside of the floor of the cranium.
  • The interior of the base of the skull (norma basalis interna) is divided into three cranial fossae, i.e., anterior, middle, and posterior. The inner aspect of the skull cap.
  • The section of the skull in the para-median plane will help us to study the nasal cavity.

Bones Of The Head And Neck Regions Skull As Seen From Above

Bones Of The Head And Neck Regions Norma Occipitalis

Bones Of The Head And Neck Regions Skull As Seen From Below

Bones Of The Head And Neck Regions Norma Lateralis

Bones Of The Head And Neck Regions Norma Frontalis

Bones Of The Head And Neck Regions Norma Frontalis

Bones Of The Head And Neck Regions Norma Basalis Interna

Bones Of The Head And Neck Regions The Base Of Skull As Seen From Internal Aspect

Superior Aspect Of The Skull (Norma Verticals)

When the skull is viewed from above it appears oval. It is relatively wider nearer its occipital pole (posteriorly). The bones forming the skullcap (roof of the brain box) are visible from this aspect.

Anterior Nasal Aperture

Bones Forming the Norma Verticalis

  • Frontal bone
  • It is a single bone that forms the anterior part of the norma verticalis.
  • Parietal bones
  • These are paired bones and lie posterior to the frontal bone on each side of the midline.

Bones Of The Head And Neck Regions The Inner Aspect Of Skull Cap

  • Occipital bone—It is a single bone and lies posterior to the parietal bones.

Sutures (Joints) Present in the Normal Verticalis

The following three sutures and their meeting points are seen in this norma:

  • Coronal suture—It lies between the frontal and right and left parietal bones.
  • Sagittal suture—It is present in the midline between the right and left parietal bones.

Norma Basalis Interna

Lambdoid suture

  • It lies between the occipital and two parietal bones.
  • Bregma—It is a landmark point, where coronal and sagittal sutures meet each other. It is present in the midline.

Lambda

  • It is present at the junction of the sagittal and lambdoid sutures.

Features of Norma Verticalis

  • The parietal foramen is present near the sagittal suture about 3.5 cm anterior to the lambda. It transmits a small emissary vein, which connects the superior sagittal sinus with the veins of the scalp.
  • Parietal eminence is the area of the maxi¬ mum convexity on the parietal bone. It is present on the posterolateral aspect of the parietal bone.
  • Superior and inferior temporal lines are seen on the lateral side of the frontal and parietal bones. The superior temporal line gives attachment to the epicranial aponeurosis and temporal fascia. The inferior temporal line gives attachment to the temporalis muscle.
  • The vertex is the highest point of the skull and is situated near the midpoint of the sagittal suture.

Applied Importance

Metopic Suture

The right and left halves of the frontal bone are ossified from separate centers. There exists a frontal suture between two frontal bones before the age of 6 years. In some adult skulls, this suture may persist in full or in part and is known; as a metopic suture.

Sutural Bones

Isolated small bony ossicles (bones) are sometimes observed along the lambdoid and sagittal sutures. These are called sutural bones. They are formed due to; ossification from separate centers

Norma Basalis Interna

Fontanelle

In the skull of a newborn there are membranous I gaps at the site of bregma and lambda. These are called anterior and posterior fontanelles respectively.

The anterior fontanelle closes (the membranous gap of the anterior fontanelle is replaced by bone) by 18 months of age, while the posterior closes by 2 to 3 months of age.

Following are the functions of fontanelle: Fontanelle allows molding of the skull during birth, as the head passes through the birth canal.

  • They also allow the brain to grow.
  • An increased intracranial tension leads to the bulging of the anterior fontanelle.
  • Similarly, depression of the anterior fontanelle indicates dehydration.
  • One can easily draw the blood for testing or inject drugs in the superior sagittal sinus through anterior fontanelle.

Bones Of The Head And Neck Regions The Presence Of Partial Metopic Suture

Bones Of The Head And Neck Regions Newborn skull as seen from above

The Posterior Aspect Of The Skull (Norma Occipitalis)

Bones Seen in Norma Occipitalis

  • Right and left parietal bones.
  • Squamous part of the occipital bone.
  • Mastoid part of the right and left temporal bone.

Norma Basalis Interna

Sutures (Joints) Seen in Norma Occipitalis

  • Posterior part of the sagittal suture in midline.
  • The lambdoid suture between two parietal and occipital bones.
  • Right and left parietomastoid sutures between the parietal and the mastoid part of the temporal bones.
  • Right and left occipitomastoid sutures between occipital and mastoid bones.
  • The parietal, occipital, and mastoid bones, on each side, meet at a point, which is known as an asterion. It is at a junction of the lambdoid, parietomastoid, and occipitomastoid sutures.

Bones Of The Head And Neck Regions Norma Occipitalis

Features

  • The external occipital protuberance is a palpable midline elevation. The highest point on this protuberance is also known as inion.
  • The superior nuchal lines extend laterally from each side of the external occipital protuberance to the mastoid process.
  • These lines mark the upper limit of the neck. The trapezius and sternocleidomastoid muscles are attached to this line.
  • The external occipital crest descends downwards from the external occipital protuberance to the foramen magnum. It gives attachment to the ligamentum nuchae. The right and left inferior nuchal lines run laterally from the crest.
  • The right and left highest nuchal lines are present just above the superior nuchal lines.
  • These lines give attachment to the epicranial aponeurosis and the occipital belly of the occipitofrontalis.
  • The mastoid foramen is situated close to the occipitomastoid suture and transmits an emissary vein and meningeal branch of the occipital artery.
  • One or more sutural bones may be present at the lambda, lambdoid suture or at asterion.
  • Between superior and inferior nuchal lines semispinalis capitis and obliquus capitis superior muscles are attached.
  • Between the inferior nuchal line and posterior margin of the foramen, magnum rectus capitis posterior major and minor are attached.

Norma Basalis Interna

Anterior Aspect Of The Skull (Norma Frontalis)

This aspect of the skull forms the facial skeleton and consists of the forehead, orbits, nasal region, malar prominence, and upper and lower jaws.

Bones Seen in the Norma Frontalis

Identify the following bones from above downwards.

  1. Frontal bone.
  2. Nasal bones.
  3. Zygomatic bones.
  4. Maxillae.
  5. Mandible.

The frontal bone and mandible are single bones, while nasal, zygomatic and maxillae are paired bones.

Sutures (Joints) Seen in the Norma Frontalis

Identify the following sutures, which are present close to the median plane:

  • The frontonasal suture is present between the nasal process of the frontal bone and nasal bones.

Bones Of The Head And Neck Regions Features of norma frontalis

  • The front-maxillary suture is present between the nasal part of the frontal bone and the frontal process of the maxilla.
  • The inter-nasal suture is present in the midline between two nasal bones above the nasal aperture.
  • The naso-maxillary suture is present between the lateral border of the nasal bone and the frontal process of the maxilla.
  • The inter-maxillary suture is present between the right and left maxilla below the nasal aperture.

Identify the following sutures present laterally in the norma frontalis:

  • The fronto-zygomatic suture is present between the zygomatic process of the frontal bone and the frontal process of the zygomatic bone. This suture is present on the lateral border of the orbit.
  • The zygomatico-maxillary suture is between the zygomatic process of the maxilla and the maxillary process of the zygomatic bone.
  • The nasion is the meeting point of internasal and frontonasal sutures. It is present in the midline at the root of the nose.

Sulcus Chiasmaticus

Features of the Norma Frontalis

For ease of understanding norma frontalis is studied under the following headings:

Forehead

  • The squamous part of the frontal bone forms the skeleton of the forehead. In the fetal and infant skulls the two halves of the frontal bone are separated by the frontal suture.
  • Two frontal bones remain separated upto 6 years of age. In some adults, this suture may persist as a metopic suture.
  • The glabella is the smooth, slightly depressed middle area just above the nasion.
  • The superciliary arches are curved elevations above the medial part of supraorbital margins. They extend laterally from glabella.
  • The frontal eminences are paired with rounded elevations above the superciliary arches.

Orbital Openings

Each orbital opening is quadrangular in shape and presents four margins.

  • The supraorbital margin is formed by the frontal bone. This border presents a supraorbital notch or foramen at the junction of medial 1/3 with lateral 2/3.
  • The supraorbital nerve and vessels pass to the forehead through the supraorbital notch or foramen. The supratrochlear vessels and nerve pass medial to the supraorbital notch.
  • The infraorbital margin is formed by the maxilla medially and zygomatic bone laterally.
  • The infraorbital foramen is present just below this margin, which transmits the infraorbital nerve and vessels.
  • The lateral margin of the orbit is formed by the zygomatic and frontal bones.
  • The medial margin is formed by the frontal bone and the frontal process of the maxilla.
  • A detailed description of the orbital cavity is given later.

Bones Of The Head And Neck Regions The orbital opening

Malar Prominence

  • The prominence of the cheek is formed by the zygomatic bone. It is situated inferolateral to the orbit.
  • The zygomatico-facial foramen is present on the bone, which transmits the nerve of the same name. Anterior Nasal Aperture The nasal aperture is piriform in shape.
  • It is bounded above by the right and left nasal bones, while lateral and inferior boundaries are formed by the nasal notches of the right and left maxilla.
  • The anterior nasal spine is a median bony projection from the maxillae.
  • Margins of the anterior nasal aperture give attachment to the nasal cartilage.
  • In the depth of the anterior nasal aperture nasal septum can be seen in the midline. This septum separates the cavity of the nose into right and left nasal cavities. A detailed description of the nasal cavity.

Sulcus Chiasmaticus

Upper Jaw (Maxillae)

The upper jaw is formed by the right and left maxilla.

  • The alveolar process of the maxilla bears the sockets for the upper teeth.
  • The root of the canine tooth produces an elevation on the upper jaw, which is known as canine eminence.
  • The canine fossa is situated just lateral to the canine eminence.
  • The incisive fossa is situated above the incisor teeth.

Lower Jaw (Mandible)

The lower jaw is formed by the mandible.

  • The mandible is the only movable bone of the skull.
  • The alveolar processes house the lower teeth.
  • The mental foramen is present below the 2nd premolÿr teeth. It gives passage to the mental nerve and vessels.
  • The anterior surface of the symphysis menti presents a triangular elevation, the mental protuberance.

Bones Of The Head And Neck Regions Margins of anterior nasal

Attachment of Muscles in the Norma Frontalis

Students should study the attachment of muscles on the norma frontalis

The Orbital Cavity

We have already studied the orbital margin in this chapter. Here, we shall study the walls and various openings of the orbital cavity.

The orbit is like a four-sided pyramid. It has a base, an apex, a roof, a floor, a medial wall, and a lateral wall.

Sulcus Chiasmaticus

The Base

The base of the orbit is the orbital opening. It has four margins, i.e., upper, lateral, medial, and inferior margins.

Bones Of The Head And Neck Regions Attachment of the muscles on norma frontalis.

Bones Of The Head And Neck Regions The orbital cavity. Schematic diagram showing walls and openings of orbit

The Apex

The apex of the orbit lies posteriorly.

The Medial Wall

The medial wall of the orbit, from anterior to posterior, is formed by the frontal process of the maxilla, lacrimal bone, orbital plate of the ethmoid, and body of the sphenoid.

  • Most anteriorly the medial wall shows a deep groove called a lacrimal groove.
  • This groove lodges the lacrimal sac. It is bounded anteriorly and posteriorly by the anterior and posterior lacrimal crests, respectively.
  • Most of the medial wall is formed by the orbital plate of the ethmoid.
  • The anterior and posterior ethmoidal foramina are present at the superior border of this bone.

The Superior Wall or Roof

The superior wall is formed mainly by the orbital plate of the frontal bone. Most posteriorly, a small part of the roof is also formed by the lesser wing of the sphenoid.

Anteromedially there is the presence of a small depression called the trochlear fossa, which gives attachment to the pulley for the superior oblique muscle.

Anterolaterally there is a deep fossa called as lacrimal fossa for lacrimal gland.

Skull Regions

The Lateral Wall

It is formed anteriorly by the zygomatic bone and posteriorly by the greater wing of the sphenoid.

The Inferior Wall or Floor

It is mainly formed by the maxilla. The small anterolateral part of the floor is also formed by the zygomatic bone. Most posteriorly the floor is formed by the orbital process of the palatine bone.

Fissures, Canals, and Foramina of the Orbital Cavity

The orbital cavity communicates with the neighboring regions of the skull through superior and inferior orbital fissures, optic and infraorbital canals, and various foramina.

It is present posteriorly between the roof and posteriorly with the pterygopalatine fossa lateral wall of the orbital cavity.

The Superior Orbital Fissure 

It is posteriorly between the infratemporal fossa. bounded above by the lesser wing of the fissure gives passage to the maxillary sphenoid, medially by the body of the sphenoid and Zygomatic nerves, emissary veins, and below and laterally by the greater wing infraorbital vessels. of the sphenoid.

The Inferior Orbital Fissures

It is present posteriorly between the lateral wall and the floor of the orbit. It is bounded above and laterally by the greater wing of the sphenoid and below and medially by the maxilla.

It communicates sphenoid and below and medially by the maxilla. It communicates The fissure gives passage to the maxillary and Zygomatic nerves, emissary veins, and infraorbital vessels.

Skull Regions

The Optic Canal

The Optic canal is present at the apex of the orbital cavity at the junction of the roof and medial wall. It is bounded medially by the body of the sphenoid and laterally by the lesser wing. It communicates with the middle cranial fossa and transmits the optic nerve along with its meningeal covering and ophthalmic artery. A common tendinous ring, which gives origin to four recti muscles of the eye, is attached surrounding the opening of the optic canal.

Bones Of The Head And Neck Regions Schematic diagram showing superior orbital fissure as seen from posterior aspect of sphenoid

Bones Of The Head And Neck Regions Schematic diagram of a Part of right orbit showing boundaries of superior and inferior orbital fissures

Bones Of The Head And Neck Regions Orbital margin and orbital cavity

Bones Of The Head And Neck Regions The margin of anterior nasal aperture

The Infraorbital Canal

The infraorbital canal is present in the bony substance of the maxilla. The canal is continuous posteriorly on the floor of the orbit as an infraorbital groove and opens anteriorly at the infraorbital foramen.

It gives passage to the infraorbital nerve and vessels. The infraorbital nerve is the continuation of the maxillary nerve.

Anterior and Posterior Ethmoidal Foramina

These two small foramina are present at the upper border of the orbital plate of the ethmoid (at the junction of the roof and medial wall of the orbit, These foramina transmit the anterior and posterior ethmoidal nerves and vessels to the anterior cranial fossa.

Skull Regions

The Lateral Aspect Of The Skull (Norma Lateralis)

This aspect of the skull is formed by cranial and facial bones. The posterosuperior region of norma lateralis (cranial part) includes the temporal fossa, external acoustic meatus, and mastoid part of the temporal bone.

The anteroinferior part of the norma lateralis (facial part) includes the zygomatic arch, infratemporal fossa, lateral aspect of the maxilla and mandible.

Bones Seen in the Norma Lateralis

Identify the following bones on the lateral aspect of the skull:

  1. Frontal.
  2. Parietal.
  3. Occipital.
  4. Nasal.
  5. Maxilla.
  6. Zygomatic.
  7. Sphenoid.
  8. Temporal
  9. Mandible

Sutures (Joints) of the Norma Lateralis

Many sutures, which are seen in this aspect, have been already observed while studying norma frontalis, verticalis, and occipitalis. Hence, we shall study the sutures present in the central region of the norma lateralis.

H Shaped Suture

  • The H-shaped suture is the meeting point of four bones, i.e., frontal, parietal, greater wing of the sphenoid, and squamous part of the temporal bone.
  • A small circular area enclosing parts of all four bones is called a “pterion”.
  • The pterion lies on the floor of the temporal fossa. The horizontal limb of the suture is the joint between the anteroinferior angle of the parietal bone and the greater wing of the sphenoid (parietosphenoid suture).
  • The greater wing of the sphenoid articulates anteriorly with the frontal bone (at front sphenoidal suture) and posteriorly with the squamous part of the temporal bone (at temporosphenoidal suture).

The Parietosquamous and Parietomastoid Sutures

The lower border of the parietal bone articulates anteriorly with the squamous part of the temporal bone at parietosquattious suture and posteriorly with the mastoid bone at the parietomastoid suture.

Lambdoid Suture

At this suture, the posterior border of the parietal bone articulates with the occipital bone.

Occipitomastoid Suture

Here the occipital bone articulates with the mastoid part of the temporal bone. Features of the Norma Lateralis Following bony features are seen on the lateral aspect of the skull:

Skull Regions

Temporal Lines

Superior and inferior temporal lines are seen in this aspect. The superior line starts at the zygomatic process of the frontal bone. It arches upwards and backward crossing the coronal suture and fades away on the temporal bone.

It gives attachment to epicranial aponeurosis and temporal fascia. The inferior line starts along with the superior and runs inferior and parallel to it. Posteriorly, it runs downwards and forwards on the temporal bone to become continuous with the supramastoid crest.

The crest is further continuous anteriorly with the posterior root of the zygoma. The inferior temporal line limits the attachment of the temporalis muscle.

Zygomatic Arch

The zygomatic arch is formed by the articulation between the temporal process of the zygomatic and the zygomatic process of the temporal bone. At the posterior end and its lower border, the zygomatic arch bears a tubercle called as root of the zygoma.

Bones Of The Head And Neck Regions Features of norma Lateralis

Here the zygomatic arch divides into anterior and posterior roots. Trace the posterior root backwards along the lateral margin of the mandibular fossa, and then above the external acoustic meatus to become continuous with the supramastoid crest.

The anterior root passes horizontally as the articular tubercle, which lies anterior to the mandibular fossa.

The temporal fascia is attached to the upper border of the zygomatic arch. The lower border and inner surface of the arch give origin to the masseter muscle.

The External Acoustic Meatus

  • The tympanic plate and squamous part of the temporal bone form the external acoustic meatus.
  • The roof and upper part of the posterior wall are formed by squamous temporal bone, while the lower part of the posterior wall, floor, and anterior wall are by the tympanic plate.
  • The margin of the meatus gives attachment to the cartilaginous part of the external acoustic meatus.

Supramental Triangle

It is a depression, situated postero-superior to the external acoustic meatus.

It is bounded above by the supra mastoid crest, in front by the posterosuperior margin of the external acoustic meatus, and behind by a vertical line drawn along the posterior margin of the meatus. Deep in this triangle lies the mastoid antrum.

Mastoid Process

The mastoid part of the temporal bone lies behind the external acoustic meatus. It is continuous above the squamous temporal bone.

The mastoid process is a downward conical projection from the mastoid part of the temporal bone. The asterion is the junctional point of three sutures, i.e., parietomastoid, occipital mastoid, and lambdoid.

The external surface of the mastoid provides attachment to the sternocleidomastoid, splenius capitis, and longissimus capitis muscles.

A mastoid foramen pierces the bone near the occipitomastoid suture. It transmits an emissary vein from the sigmoid sinus and the meningeal branch of the occipital artery.

Skull Regions

The Styloid Process

  • The styloid process is seen when the skull is viewed from the lateral side. It is about a 2 to 5 cm long process projecting downwards, forwards, and medially.
  • It is situated in front of the mastoid process on a deeper plane. It gives attachment to the styloglossus, stylohyoid, and stylopharyngeus muscles. The stylohyoid and stylomandibular ligaments are also attached to it.

Temporal Fossa

This is a shallow fossa that lies above the zygomatic arch. The temporalis muscle is located in this fossa.

This fossa is bounded:

  • Posteriorly and superiorly by temporal lines.
  • Anteriorly by the temporal surface of the frontal and zygomatic bones.
  • Interiorly by the superior border of the zygomatic arch and supramastoid crest (on the lateral side). Interiorly on the medial side by the infratemporal crest of the greater wing of the sphenoid.
  • Between zygomatic arch and infratemporal crest temporal fossa communicates below with the infratemporal fossa.
  • Floor of the temporal fossa is formed by the part of the frontal, parietal, temporal and greater wing of the sphenoid bones. The circular area enclosing all these four bones and H shaped suture is called as pterion.
  • It is situated 4 cm above the mid point of the zygomatic arch and 3.5 cm behind the frontozygomatic suture.
  • The middle meningeal vein, anterior branch of middle meningeal artery, and stem of the lateral sulcus of brain lie deep to the pterion.
  • The contents of the temporal fossa are temporalis muscle, deep temporal vessels and nerves and zygomaticotemporal nerve.

Infratemporal Fossa

It is an irregular fossa below the zygomatic arch and behind the maxilla. It communicates above with the temporal fossa deep into the zygomatic arch.

Bones Of The Head And Neck Regions Lateral wall of infratemporal fossa

Boundaries

  • Anterior wall: The posterior surface of the body of the maxilla bone. The surface of the maxilla shows many perforations (openings) for posterosuperior alveolar nerves and vessels.
  • Medial wall: It is formed by the lateral pterygoid plate and pyramidal process of palatine bone. The junction of the anterior and medial walls shows a fissure called a term gomaxillaiy fissure. Deep to the fissure lies the pterygopalatine fossa.
  • Lateral wall: It is formed by the ramus and coronoid process of the mandible.
  • Roof: The roof is formed by the temporal surface of the greater wing of the sphenoid. At the junction of the roof and anterior wall, lies the lateral part of the inferior orbital fissure through which the infratemporal fossa communicates with the orbit Foramen ovale and foramen spinosum are present in the roof of the infratemporal fossa.
  • Floor: It is not bounded but open.
  • Posterior wall: It is also open.

Bones Of The Head And Neck Regions Suprameatal triangle

Bones Of The Head And Neck Regions Infratemporal fossa, roof and anterior wall, as seen from inferior aspect

The contents of the infratemporal fossa are as mentioned below:

  • Lateral and medial pterygoid muscles and lower part of the temporalis.
  • The maxillary artery and its branches, pterygoid venous plexus.
  • Mandibular, maxillary and chorda tympani nerve and otic ganglion.

Skull Regions

Pterygopalatine Fossa

It is a small pyramidal space situated below the apex of the orbit and deep to the pterygomaxillary fissure.

Boundaries

Anterior: Posterior surface of the body of the maxilla.

Posterior: Root of the pterygoid process and the anterior surface of the greater wing of the sphenoid.

Medial: The perpendicular plate of the palatine bone.

Lateral: It is open and communicates with the infratemporal fossa through the pterygo¬ maxillary fissure. (The pterygomaxillary fissure is a triangular gap bounded anteriorly by the maxilla and posteriorly by the pterygoid process.

It transmits the third part of the maxillary artery, maxillary nerve, and posterior superior alveolar nerve and vessels).

Roof: Medially it is bounded by the body of the sphenoid and orbital process of the palatine bone. Laterally it communicates with the inferior orbital fissure.

Floor: It is closed due to the fusion of the anterior and posterior walls.

Bones Of The Head And Neck Regions Infratemporal fossa seen after removal of zygomatic arch and mandible.

Communications of the Pterygopalatine Fossa

It communicates with the following:

  • The orbit-Through the infraorbital fissure.
  • The infratemporal fossa-Through pterygomaxillary fissure.
  • The nasal cavity-Through sphenopalatine foramen.
  • The middle cranial fossa-Through the foramen rotundum.
  • The foramen lacerum—Through pterygoid canal.

Contents of the Pterygopalatine Fossa

  • Maxillary nerve, pterygopalatine ganglion and its branches.
  • The third part of the maxillary artery.

The Norma Basalis Externa

To visualize the base of the skull, it is necessary to detach the mandible from the rest of the skull. The base of the skull is formed, from anterior to posterior, by maxillae, palatine, vomer, sphenoid, temporal and occipital bones.

For the convenience of description, the norma basalis is divided into anterior, middle, and posterior parts by two imaginary horizontal lines.

The first imaginary horizontal line is drawn along the posterior border of the hard palate and the second line passes through the anterior margin of the foramen magnum.

Anterior Part of the Norma Basalis Externa

It is formed by the alveolar arch of the maxilla and hard palate.

Bones Of The Head And Neck Regions The anterior part of norma basalis externa. Some parts of middle portion are also shown

Alveolar Arch

The alveolar arch is formed by the alveolar processes of the right and left maxillae. It is horseshoe-shaped and possesses the sockets for the roots of the teeth of the upper jaw.

Skull Regions

Hard Palate

  • The hard palate lies within the alveolar arch.
  • The anterior 2/3 of the hard palate is formed by the palatine processes of the right and left maxillae.
  • The posterior 1/3 is formed by the horizontal plates of palatine bones.

Hard Palate Features

Sutures (joints) and foramina are seen in the anterior part of the norma basalis.

Intermaxillary, interpalatine, and palato maxillary sutures. All the above three sutures are collectively called cruciform sutures.

The Greater Palatine Foramen

  • It is situated just medial to the third molar, posterior to the palatomaxillary suture.
  • A groove rims forward from this foramen. This foramen transmits greater palatine vessels and nerves.

The Lesser Palatine Foramina

  • These are two to three small foramina situated behind the greater palatine foramen. These foramina are present in the pyramidal process of the palatine bone.
  • The lesser palatine vessels and nerves pass through these foramina. The Incisive Fossa It is a triangular depression in the median plane behind the central incisor teeth.
  • The right and left lateral walls of the fossa bear lateral incisive foramen, which communicate with the floor of the nasal cavity. It gives passage to the nasopalatine nerve and greater palatine vessels.
  • Pyramidal Process of the Palatine Bone It occupies the gap between the lower end of the medial and lateral pterygoid plates.

The Posterior Nasal Spine

It is a midline projection from the posterior border of the hard palate. It gives attachment to the musculus uvulae on each side.

Palatine Crest

It is a curved ridge a little in front of the posterior border of the hard palate. It gives attachment to the palatine aponeurosis and the tendon of tensor veli palatini.

Premaxilla

It is a triangular piece of maxilla holding four incisor teeth. In young persons a suture may be seen running from the posterior part of the incisive fossa laterally between the lateral incisor and canine teeth, separating the premaxilla from the rest of the maxilla.

The Middle Part of the Norma Basalis Externa

The middle part extends between two imaginary lines, i.e., the anterior line drawn along the posterior border of the hard palate and a posterior line drawn along the anterior margin of the foramen magnum.

The structures present in the region are divided into median areas and right and left areas.

The bones present in the median area, from anterior to posterior are

Bones Of The Head And Neck Regions The middle part of norma basalis externa. Some part of anterior and posterior portions of norma basalis are also shown

  • The posterior border of the vomer.
  • Body of sphenoid.
  • Basilar part of the occipital bone.

The bones in the lateral area are:

  • Medial and lateral pterygoid plates on the right and left side. These plates are the part of the sphenoid bone.
  • The infratemporal surface of the greater wing of the sphenoid. It is situated lateral to the pterygoid plates.
  • Temporal bone with its squamous, tympanic, and petrous parts.

Posterior Nasal Apertures and Related Structures Features

The Posterior Nasal Apertures and Related Structures These are quadrilateral in shape and situated above the posterior margin of the hard palate.

  • The posterior border of the vomer separates the right and left apertures from each other, thus forming the medial boundary of each aperture.
  • The superior surface of the horizontal plate of palatine bone forms the floor of the posterior nasal aperture.
  • Laterally, each aperture is bounded by the perpendicular plate of palatine bone, which articulates with the medial pterygoid plate, posteriorly.
  • The roof of the aperture is formed by the ala of the vomer and the sphenoidal process of the palatine bone.

The upper border of the vomer splits into two alae close to the inferior surface of the body of the sphenoid.

The midline groove between two alae of the vomer articulates with the sphenoidal rostrum (which is a midline ridge on the inferior surface of the body of the sphenoid).

The undersurface of the ala of the vomer, on each side, is overlapped by the vaginal process, which arises from the root of the medial pterygoid plate.

There exists a narrow vomer original canal between the undersurface of the ala of the vomer and the upper surface of the vaginal process.

It is present occasionally and gives passage to the pharyngeal vessels and nerves. From the upper end of the perpendicular plate of the palatine bone, there extends a sphenoidal process medially, which overlaps the undersurface of the vaginal process.

A narrow canal is present between the undersurface of the vaginal process and the superior surface of the sphenoidal process.

It is called as palatinovaginal canal and gives passage to the pharyngeal vessels and nerves. The vomerovaginal canal is situated posteriorly as compared to the palatinovaginal canal.

Bones Of The Head And Neck Regions Schematic diagram showing the bones Forming Posterior Nasal Aperture

The Median Bar of Bone

  • Just behind the alae of vomer bone there is the presence of a broad bar of bone in the midline. It extends upto the foramen magnum. It is formed by two bones, i.e.,
  • Under the surface of the body of the sphenoid and basilar part of the occipital bone. These two bones (body of sphenoid and occipital bone) remain separated from each other by a cartilaginous synchondrosis joint which later fuses at about 25 years of age.
  • A median elevation is seen just in front of the foramen magnum. It is known as the pharyngeal tubercle, which gives attachment to pharyngeal raphae and fibers of the superior constrictor.
  • Note the attachment of longus capitis and rectus capitis anterior on the basilar part of the occipital bone.

Pterygoid Processes

  • Each pterygoid process descends vertically downwards from the junction of the body and the greater wing of the sphenoid.
  • The anterior surface of the root of the pterygoid process forms the posterior wall of the pterygopalatine fossa.
  • The pterygoid process consists of medial and lateral pterygoid plates.
  • The pterygoid plates unite anteriorly and enclose a fossa (pterygoid fossa), which faces posterolaterally.
  • The anterior surface of the fused medial and lateral pterygoid plates form the posterior boundary of the pterygomaxillary fissure.
  • At the lower end, a gap between medial and lateral pterygoid plates is occupied by the pyramidal process of the palatine bone

The Medial Pterygoid Plate

  • Trace above the posterior border of the medial pterygoid plate. It ends in a small fossa the “scaphoid fossa”. It gives attachment to the tensor veli palatini.
  • The lower end of its posterior border projects downwards and laterally as a hook, the hamulus. Around the hamulus, the tendon of tensor veli palatini turns medially to enter the soft palate. The hook of the hamulus also gives attachment to the pterygomandibular raphe.
  • Its posterior border gives attachment to the pharynx basilar fascia.
  • An angular process (process tubarius) projects backward from the middle of the posterior border of the medial pterygoid plate. This process supports the medial end of the auditory tube.
  • The lower end of the posterior border with the pterygoid hamulus gives origin to the superior constrictor muscle.

Bones Of The Head And Neck Regions Attachment of muscles on norma basalis Externa

The Lateral Pterygoid Plate

  • The medial surface of the lateral pterygoid plate gives origin to the deep head of the medial pterygoid muscle.
  • Its lateral surface gives origin to the lower head of the lateral pterygoid muscle.

Infratemporal Surface of the Greater Wing of Sphenoid

This surface of the greater wing of the sphenoid extends laterally from the root of the lateral pterygoid plate. It is pentagonal and forms the roof of the infratemporal fossa.

  • Anteriorly it forms the posterolateral border of the inferior orbital fissure.
  • Laterally the surface is limited upto the infratemporal crest. Beyond this crest, the greater wing extends to the temporal surface.
  • Postero-laterally it articulates with the squamous part of the temporal bone.
  • Posteromedially it articulates with the petrous part of the temporal bone. At the junction of these two bones, a sulcus is formed, which is known as sulcus tubae.

The sulcus lodges the cartilaginous part of the auditory tube

The posterior-most of this bone projects down as the spine of the sphenoid.

The spine of the sphenoid gives attachment to:

Ligaments-Sphenomandibular, pterygospinous, and anterior ligament of the malleus.

Muscles-Posterior fibers of tensor veli palatine.

Related structures- Auriculotemporal nerve (laterally) chorda tympani nerve and auditory tube (medially).

The infratemporal surface of the greater wing of the sphenoid gives origin to the upper head of the lateral pterygoid muscle.

This surface presents two foramina, i.e., foramen ovale and spinosum. The foramen ovale is oval and presents posterolateral to the root of the lateral pterygoid plate. Foramen spinosum is small rounded foramen situated posterolateral to foramen ovale.

It is present anteriomedial to the spine of the sphenoid. Sometimes a small foramen may be seen medial to the foramen ovale, emissary sphenoidal foramen.

The Infratemporal Surface of the Squamous Part of the Temporal Bone This part is present posterolateral to the greater wing of the sphenoid and along with the infratemporal surface of the greater wing of the sphenoid it also forms the roof of the infratemporal fossa.

When a zygomatic process is traced backward this surface presents a tubercle (tubercle of the root of zygoma) where the zygomatic process divides into anterior and posterior roots.

The anterior root runs medially anterior to the mandibular fossa and bears an articular tubercle.

The posterior root forms the lateral boundary of the mandibular fossa. Behind the articular tubercle, the mandibular fossa is deep depression.

Both the articular tubercle and mandibular fossa, are articular and articulates with the head of the mandible.

The posterior part of the mandibular fossa is non-articular and formed by the tympanic plate of the temporal bone.

Bones Of The Head And Neck Regions The infratemporal surface of the greater wing of sphenoid (G.W.S.) and squamous temporal bone

The Tympanic Part of the Temporal Bone

  • The tympanic plate forms the anterior wall, floor, and lowermost part of the posterior wall of the external acoustic meatus.
  • The squamous part of the temporal bone and tympanic plate unite with each other at the squamotympanic fissure, which is present on the floor of the mandibular fossa.
  • The tegmen tympani part of the petrous temporal bone may project in the medial part of the squamotympanic fissure.
  • The presence of the tegmen tympani divides the squamotympanic fissure into a petrosquamous fissure and a petrotympanic fissure.
  • The petro-tympanic fissure gives passage to chorda tympani nerve, anterior tympanic artery and anterior ligament of malleus.

The Inferior Surface of Petrous Part of the temporal bone

The petrous part of the temporal bone is situated behind the greater wing of the sphenoid and lateral to the body of the sphenoid and basilar part of the occipital bone.

The apex of the bone is separated from the body of the sphenoid, the root of the pterygoid process, and the basilar part of the occipital bone by the foramen lacerum.

The carotid canal opens in the posterior wall of the foramen lacerum, while the pterygoid canal opens into its anterior wall. The upper part of the foramen lacerum is traversed by the internal carotid artery.

The nerve to the pterygoid canal is formed in the foramen lacerum by the union of the greater superficial petrosal and deep petrosal nerves. The nerve then passes through the pterygoid canal and enters the pterygopalatine fossa.

A quadrilateral area behind the apex of the petrous bone gives origin to tire levator veli palatini.

The lower opening of the carotid canal is situated just behind the quadrilateral area the inferior surface of the petrous temporal bone.

It transmits the internal carotid artery. Posterior to the lower opening of the carotid canal there lies the jugular fossa.

The sulcus tube is a groove, which lies between the posteromedial margin of the greater wing of the sphenoid and the petrous part of the temporal bone. It is occupied by the cartilaginous part of the auditory tube.

The Posterior Part of the Norma Basalis Externa

  • The posterior part lies behind the imaginary line drawn along the anterior margin of the
    foramen magnum. This part is also divided into median area and two lateral areas:
  • The median area consists of the foramen magnum and the squamous part of the occipital bone behind it.
  • The condylar parts of the occipital bone are present on either side of the foramen magnum.
  • The basilar part of the occipital bone lies anterior to the foramen magnum The bones in the lateral area, on each side, are the mastoid and styloid process.

The Median Area

The foramen magnum is large and oval. It connects the posterior cranial fossa above with the vertebral canal below.

The Basilar Part

The basilar part of the occipital bone is in The basilar part of the occipital bone is in sphenoid bone. These two bones are separated from each other by a primary cartilaginous joint in young but fuse in adults.

The pharyngeal tubercle is a small tubercle present on the inferior is a small tubercle present on the inferior attachment to the pharyngeal raphe.

Bones Of The Head And Neck Regions The posterior part of the norma basalis externa

Bones Of The Head And Neck Regions Schematic diagram showing structure passing through foramen magnum

The Foramen Magnum

The alar ligaments, which are attached to the lateral margins of the foramen magnum, divide the foramen into small anterior and large posterior parts.

The structures passing through the anterior and posterior parts are shown. The anterior and posterior margins of the foramen magnum give attachment to the anterior and posterior atlanto-occipital membranes respectively.

The Condylar Parts

The condylar parts of the occipital bone consist of right and left occipital condyles, which are situated on each side of the foramen magnum. The jugular process is present lateral to each condyle. The condyles are set obliquely and their inferior surface is convex and articular.

Each condyle articulates with the corresponding upper surface of the lateral mass of the atlas vertebra (superior articular facet) to form an atlantooccipital joint.

There is an opening of the hypoglossal or anterior condylar canal on the lateral border of the condyle near its anterior end. It gives passage to the hypoglossal nerve, emissary vein, and meningeal branch of the ascending pharyngeal artery.

A condylar fossa is present posterior to each condyle which may show the presence of a canal which may show the presence of a canal to the emissary vein which connects the sigmoid sinus to occipital veins.

The jugular process articulates laterally with the petrous temporal bone by a primary cartilaginous joint. The anterior margin of the jugular process is free and known as the jugular notch. The jugular notch forms the posterior boundary of the jugular foramen.

The Jugular Foramen

  • This irregular large foramen is bounded anteriorly by the posterior border of the petrous temporal bone and posteriorly by the jugular notch of the jugular process of the occipital bone.
  • It is divided into anterior, middle, and posterior parts. The posterior part of the jugular foramen presents a jugular fossa, which is due to the presence of depression in the petrous temporal bone.
  • The mastoid canaliculus is an opening of a minute canal in the lateral wall of the jugular fossa which transmits the auricular branch of the vagus.
  • The tympanic canaliculi are present on the ridge between the jugular fossa and the lower opening of the carotid canal. The structures pass through three divisions of the jugular foramen.

Bones Of The Head And Neck Regions Anterior and part of middle portion of norma basalis externa

Bones Of The Head And Neck Regions Part of middle and posterior part of norma basalis externa

Bones Of The Head And Neck Regions Schematic diagram showing structures Passing Through Three Divisions Of Left Jugular Foramen

The Squamous Part ligament

This part lies behind the foramen magnum. In the midline, there extends an external occipital crest between the foramen magnum and the external occipital protuberance.

The upper end of the ligamentum nuchae is attached to the crest and protuberance. The superior and inferior nuchal lines and attachment of muscles in this area have already been described in “norma occipitalis”.

The Lateral Area

  • In the lateral area, there are three important structures, i.e., styloid process, mastoid process, and stylomastoid foramen.
  • Styloid Process It is a long conical process, which projects downwards, forwards, and medially below the tympanic part of the temporal bone.
  • It lies lateral to the jugular fossa.
  • It gives attachment to 3 muscles and two ligaments.
  • It is related laterally to the parotid gland and medially to the internal jugular vein.
  • Near its base, it is crossed by the facial nerve.

Mastoid Process

  • It is a conical projection from the mastoid part of the temporal bone. The mastoid process is situated posterolateral to the styloid process.
  • A deep groove (digastric groove) is seen on its medial aspect, which gives attachment to the posterior belly of the digastric muscle.

Stylomastoid Foramen

The stylomastoid foramen is present between styloid and mastoid processes, i.e., posterolateral to the styloid process and anteromedial to the mastoid process. The stylomastoid artery and facial nerve pass through it.

Bones Of The Head And Neck Regions Attachments of the styloid process

The Interior Of The Skull

  • When the upper part of the vault of the skull (skull cap or calvaria) is removed we may see the inner surface of the cranial vault and the interior of the base of the skull.

Inner Surface of the Cranial Vault

  • The various bones and the intervening sutures forming the cranial vault are the same as observed in the norma verticalis.
  • The frontal crest is the midline structure present most anteriorly
  • A groove extends anteroposteriorly in the median plane, from the frontal crest to the internal occipital protuberance. This groove is known as the sagittal sulcus.
  • The superior sagittal sinus is lodged in the sagittal sulcus. At the internal occipital protuberance, this sinus becomes continuous with the right transverse sinus.
  • The frontal crest and the margins of the sagittal sulcus give attachment to the falx cerebri.
  • Many small depressions {granular pits) are observed on each side of the sagittal sulcus. These are produced by the arachnoid granulations. Their number increases with the increasing age.
  • Note the presence of parietal foramen on either side of the sagittal suture about 3.5 cm anterior to lambda. These foramina transmit emissary veins.
  • The inner aspect of the calvaria shows the presence of grooves for the meningeal vessels. These grooves run backward and upwards from the anteroinferior angle of the parietal bone.

Bones Of The Head And Neck Regions The inner surface of cranial vault

Interior of the Base of the Skull

The internal aspect of the base of the skull (norma basalis internal) as seen after the removal of the skull cap, can be divided into three fossae, i.e., anterior, middle, and posterior cranial fossae

The Anterior Cranial Fossa

Bones of the Anterior Cranial Fossa The anterior cranial fossa is formed by the frontal bone, cribriform plate of the ethmoid, lesser wing of the sphenoid, and the anterior part of the superior surface of body of the sphenoid (jugum sphenoidal).

Sutures of the Anterior Cranial Fossa

With the help of identifying frontoethmoidal, frontosphenoidal, and sphenoethmoidal sutures.

Borders

The anterior and lateral boundaries of the fossa are formed by the frontal bone.

The posterior boundary is formed by the posterior border of the lesser wing of the sphenoid, the anterior clinoid process, and the anterior border of the sulcus chiasmaticus.

Floor

In the median region, the floor is formed by the cribriform plate of ethmoid and jugum sphenoidal.

While, the lateral region of the floor is formed by the orbital plates of the frontal bone and the lesser wings of the sphenoid, on each side.

Bones Of The Head And Neck Regions The base of anterior cranial fossa. The adjacent part of middle cranial fossa is also shown

Median Area of the Floor

  • The most anterior structure in the midline is the frontal crest.
  • Posterior to the frontal crest a triangular process, the crista galli, is seen. It projects upwards from the cribriform plate and provides attachment to the falx cerebri.
  • Between the frontal crest and crista galli identify the foramen caecum. Sometimes it transmits a vein from the nasal mucosa to the superior sagittal sinus.
  • The cribriform plate of ethmoid is present on either side of the crista galli between the orbital plates of the frontal bone. The cribriform plate separates the anterior cranial fossa from the nasal cavity.
  • It presents many small apertures through which pass the olfactory nerves from the nasal mucosa to the olfactory bulb.
  • On each side of the cribriform plate, there is an opening of the anterior and posterior ethmoidal canals.
  • The anterior canal transmits anterior ethmoidal vessels and nerves, while the posterior canal transmits only posterior ethmoidal vessels.
  • Posterior to the cribriform plate the median area of the floor is formed by jugum sphenoidale of the body of the sphenoid. It forms the roof of the sphenoidal air sinus. Lateral Area of the Floor On each side it consists of an orbital plate and a lesser wing of the sphenoid.
  • The orbital plate of the frontal bone lies lateral to the cribriform plate on either side. It is convex and shows the impre¬ ssions of cerebral gyri.
  • Laterally it forms the roof of the orbit and medially the roof of the ethmoidal sinuses. Posteriorly, the orbital plates articulate with the anterior margin of the lesser wing of the sphenoid.
  • The lesser wings of the sphenoid are continuous with the jugum sphenoidale medially. The posterior margin of the lesser wing is free and concave. It is related to the sphenoid-parietal sinus.
  • The medial end of the posterior margin ends into the anterior clinoid process, which gives attachment to the free margin of tentorium cerebelli.

Middle Cranial Fossa

The middle cranial fossa is narrow in the middle and expanded laterally. It lodges hypophysis cerebri in the middle and temporal lobes of the brain on each side.

Boundaries

  • The anterior boundary of the middle cranial fossa separates the anterior and middle fossae from each other.
  • It is formed by the posterior border of the lesser wing of the sphenoid, anterior clinoid process and anterior border of the sulcus chiasmaticus.
  • The posterior boundary separates it from the posterior cranial fossa.
  • It is formed by the superior border of the petrous part of the temporal bone, posterior clinoid process, and dorsum sellae.
  • On each side, the middle cranial fossa is bounded by the greater wing of the sphenoid, the squamous part of the temporal bone, and the parietal bone.

The floor of the Middle Cranial Fossa

It is shaped like a butterfly and consists of median and lateral parts.

Median Part of the Floor of the Middle Cranial Fossa

  • The median part is formed by the body of the sphenoid. Most anteriorly sulcus chiasmaticus is present.
  • It is a transverse groove, which becomes continuous laterally with the optic canal. The optic chiasma lies posterior to this groove.
  • Each optic canal opens into orbit thus connecting the middle cranial fossa with orbit.
  • It is bounded by anterior and posterior roots of the lesser wing and body of the sphenoid. This canal gives passage to the optic nerve, meninges, and ophthalmic artery.
  • Behind the sulcus chiasmaticus, a saddle-shaped depression is present on the superior surface of the body of the sphenoid. It is known as sella turcica.
  • The sella turcica consists of tuberculum shellac, hypophyseal fossa, and dorsum sellae from anterior to posterior. The tuberculum sellae is the median elevation just behind the sulcus chiasmaticus.
  • It receives the attachment of the anterior margin of the diaphragm sellae. The hypophyseal fossa is a deep depression posterior to the tuberculum sellae. It lodges hypophysis cerebri. Deep to the hypophyseal fossa lies the sphenoidal air sinus.
  • The dorsum sellae is a square-like vertical plate of bone posterior to the hypophyseal fossa. The superior border of the dorsum sellae, on each side forms the posterior clinoid process which gives attachment to the attached margin of the tentorium cerebelli. While the superior border itself gives attachment to the posterior margin of diaphragma sellae.

Bones Of The Head And Neck Regions The floor of middle cranial fossa

  • On each side of the body of the sphenoid, there is the presence of a shallow groove called a carotid groove. This groove extends from the foramen lacerum to the medial side of the anterior clinoid process. It lodges the internal carotid artery.

Lateral Part of the Floor of Middle Cranial Fossa

Laterally the floor of the middle cranial fossa is formed by three bones, i.e., the cranial surface of the greater wing of the sphenoid, and squamous, and petrous parts of the temporal bone. Following fissures, foramina, and grooves are observed on the floor of the fossa.

The superior orbital fissure is a triangular oblique cleft present most anteriorly in the middle cranial fossa. It connects the middle fossa with the orbit.

The fissure is bounded above by the lesser wing of the sphenoid, below by the greater wing, and medially by the body of the sphenoid.

We have already seen that the fissure is divided into three parts by the attachment of a tendinous ring on the orbital surface of the fissure. The structures pass through three subdivisions of the superior orbital fissures.

The foramen rotundum is situated in the greater wing of the sphenoid just inferomedial to the medial end of the superior orbital fissure.

It opens anteriorly into the pterygopalatine fossa and transmits the maxillary nerve.

The foramen ovale is situated in the greater wing of the sphenoid posterolateral to the foramen rotundum. It opens into the infratemporal fossa and transmits the mandibular nerve.

The foramen spinosum is also present in the greater wing of the sphenoid, posterolateral to the foramen ovale, and communicates with the infratemporal fossa.

It gives passage to the middle meningeal artery and other structures.

Sometimes the emissary sphenoidal foramen is present between foramen rotundum and foramen ovale.

It transmits the emissary vein. Similarly, sometimes a foramen is present between foramen ovale and spinosum, which transmits lesser petrosal nerve. It is called as foramen innominatum.

Bones Of The Head And Neck Regions Structures passing through right superior orbital fissure

Bones Of The Head And Neck Regions Anterior and part of middle portion of norma basalis Interna

Bones Of The Head And Neck Regions Norma Basalis Interna

The foramen lacerum is situated posteromedial to foramen ovale, between the body of the sphenoid and the apex of the petrous temporal bone.

The carotid canal opens in its posterolateral part. The carotid artery traverses the upper part of the foramen lacerum. The pterygoid canal opens in its anterior margin and gives passage to the nerve of the pterygoid canal.

In the lateral part of the floor, the markings of the middle meningeal vessels are seen. The groove runs forward and laterally from the foramen spinosum and later divides into two anterior and posterior branches of the middle meningeal artery.

The anterior surface of the petrous temporal bone forms the posterior wall of the middle cranial fossa. Near the apex, a shallow depression is seen. It is known as trigeminal impression for the trigeminal ganglion.

Arcuate eminence is a prominent elevation deep to which lies the superior semicircular canal.

The area lateral to the eminence is formed by the thin plate of bone called tegmen tympani.

This forms the roof of the middle ear cavity and auditory tube. The anterior surface of the petrous temporal bone presents two grooves running downwards and medially.

The upper and medial groove begins at the hiatus for the greater superficial petrosal nerve and runs towards the foramen lacerum. It lodges a greater superficial petrosal nerve.

The lower and lateral groove begins at the hiatus for the lesser petrosal nerve and runs towards the foramen ovale.

It lodges lesser petrosal nerves.

The superior border of the petrous bone is grooved for the lodgement of the superior petrosal sinus. Near the apex of the petrous temporal bone, this border is 184 crossed by the trigeminal nerve. This border also gives attachment to the tentorium cerebelli.

Posterior Cranial Fossa

The posterior cranial fossa is the deepest of the three fossae and lodges the hindbrain (cerebellum, pons, and medulla).

Bones Forming the Posterior Cranial Fossa

  • Posterior part of the body of the sphenoid.
  • Occipital bone.
  • The posterior surface of the petrous temporal bone.
  • Mastoid part of the temporal bone.
  • Posteroinferior angle of parietal bone.

Sutures and Fissures of the Posterior Cranial Fossa

  • The lower end of lambdoid suture between parietal and occipital bone.
  • The parieto-mastoid suture.
  • The occipito-mastoid suture.
  • Petro-occipital suture.

Boundaries

The middle and posterior cranial fossa are separated from each other by the dorsum sellae, posterior clinoid process, and superior border of the petrous temporal bone.

On the lateral side, this fossa is bounded by the mastoid part of the temporal bone and the postero-inferior angle of the parietal bone.

Posteriorly, it is bounded by the squamous part of the occipital bone. The Floor of the Posterior Cranial Fossa The floor can be divided into median and lateral parts.

Bones Of The Head And Neck Regions The floor of the posterior cranial fossa

The Median Part of the Floor

The median part of the floor presents the most striking structure, i.e., the foramen magnum.  The part anterior to the foramen magnum is called as clivus. The parts posterior to the foramen magnum are the internal occipital crest and internal occipital protuberance.

  • The clivus is the sloping surface of the bone formed by the fusion of the basal part of the occipital bone and the body of the sphenoid.
  • The lateral border of the basilar part of the occipital bone is separated by the petrous temporal bone by a petrooccipital fissure, which lodges the inferior petrosal sinus.
  • The basilar part of the clivus gives attachment to the membrane tectoria, the upper band of the cruciate ligament, and the apical ligament of dens.
  • The foramen magnum is a large oval-shaped central opening on the floor of the posterior fossa. Structures passing through this foramen.
  • On each side of the foramen magnum, the inner opening of the hypoglossal canal lies just above its lateral margin. It transmits the hypoglossal nerves and vessels. The jugular tubercle is situated between the jugular foramen and the hypoglossal canal.
  • It is related to the 9th, 10th, and 11th cranial nerves. Sometimes the posterior condylar canal is also present behind the jugular foramen and lateral to the jugular tubercle. It transmits the emissary vein.
  • The internal occipital crest is a ridge present in the midline, which extends between the foramen magnum and internal occipital protuberance. It gives attachment to the falx cerebelli.
  • The internal occipital protuberance is situated opposite the external occipital protuberance. On each side, it is related to the transverse sinus. It is also related to the confluence of dural venous sinuses.

The Lateral Part of the Floor

  • The posterior surface of the petrous temporal bone, in its middle, shows the opening of the internal acoustic meatus.
  • It transmits the facial and vestibulocochlear nerves and labyrinthine vessels. Posterolateral to the internal meatus there lies an oblique slit which leads upwards into a canal called the aqueduct of the vestibule. It lodges succus and ductus endolymphaticus.
  • The right and left transverse sulci run laterally from each side of the internal occipital protuberance. The right sulcus is more prominent. The transverse sulcus lodges the transverse sinus.
  • Each transverse sulcus curves downwards at the mastoid angle of the parietal bone as the sigmoid sulcus. The sigmoid sulcus runs downwards and medially with an S-shaped curve.
  • It grooves the petrous and mastoid part of the temporal bone to reach the posterior end of the jugular foramen.
  • The jugular foramen is situated between the posterior end of the petro-occipital fissure and the terminal end of the sigmoid sulcus Above it is bounded by the petrous temporal bone and below by the jugular process of the occipital bone. It is divided into anterior, middle, and posterior parts.

Bones Of The Head And Neck Regions Structure passing through various foramina of the floor of cranial Fossae

Bones Of The Head And Neck Regions Structure passing through optic canal

Bones Of The Head And Neck Regions Structures Passing Through The base Of The Skull (Norma basalis Externa )

Bones Of The Head And Neck Regions Structures passing through right infraorbital fissure

Nasal Cavity

The nasal cavity is divided into right and left halves by vertical median septum (i.e., the nasal septum). Each half of the cavity consists of an anterior opening, i.e., the anterior nasal aperture, a posterior nasal aperture, a lateral wall, a medial wall, a roof, and a floor.

Anterior and Posterior Nasal Apertures

The anterior nasal apertures open on the norma frontalis, while both posterior nasal apertures open on the base of the skull just above the posterior margin of the bony palate.

The Medial Wall

The medial wall, anterosuperiorly, is formed by the perpendicular plate of the ethmoid. While posteroinferiorly it is formed by the vomer bone. In the living condition, the anterior gap in the bony septum is filled by septal cartilage.

Bones Of The Head And Neck Regions Schematic diagram showing roof, floor, medial and lateral walls of nasal cavity

Bones Of The Head And Neck Regions Margins of anterior nasal

Bones Of The Head And Neck Regions Schematic diagram showing the bones Forming Posterior Nasal Aperture

The Lateral Wall

The lateral wall is formed by three irregular bony projections, i.e., superior, middle, and inferior conchae.

These conchae run anterol posteriorly and lie one above the other. The spaces deep into the conchae are called meatuses, i.e., superior, middle, and inferior meatuses. The area above the superior concha is called a sphenoethmoidal recess. The following bones form the lateral wall of the nose.

Bones Of The Head And Neck Regions The medial wall of the nasal cavity

  • Ethmoid—The superior and middle conchae are part of the ethmoid bone.
  • The inferior concha is a separate bone.
  • Perpendicular plate of the palatine bone.
  • Maxilla—All the above three bones are attached to the nasal surface of the maxilla.
  • A part of the nasal surface of the maxilla remains free on the anterior and inferior part of the lateral wall of the nose

Roof

From anterior to posterior, the roof is formed by nasal bone, frontal bone, cribriform plate of the ethmoid, anterior surface of a body of the sphenoid, and ala of the vomer.

The nasal cavity communicates with the anterior cranial fossa through numerous apertures in the cribriform plate of the ethmoid bone.

Floor

It is formed by the palatine process of It is formed by the palatine process of In the anterior part of the floor there is the upper opening of the incisive canal.

Bones Of The Head And Neck Regions The lateral wall of nasal cavity as seen before removal of nasal concha

Bones Of The Head And Neck Regions The lateral wall of nasal cavity as seen after removal of nasal conchae

Further Details of Lateral Wall

Sphenoethmoidal Recess

It is situated above the superior concha and receives the opening of the sphenoid air sinus.

Superior Meatus

It is situated between the superior and middle conchae. It receives the opening of the posterior ethmoidal sinuses.

Bones Of The Head And Neck Regions Bony Nasal Septum

Bones Of The Head And Neck Regions Lateral Bony Wall Of Nasal Cavity

Middle Meatus

It is situated between the middle and inferior conchae. Deep to middle concha is a rounded prominence called the bulla ethmoidale.

It is produced by the middle ethmoidal air sinuses. The middle ethmoidal sinuses open on the bulla.

Antero-inferior to the bulla is a curved plate of bone called an uncinate process. It runs downwards and backward. The curved space between the uncinate process and bulla is called hiatus semilunaris. The hiatus semilunaris is continuous above and anteriorly into the infundibulum.

The infundibulum is continuous with the frontal air sinus. The anterior ethmoidal sinus also opens in the infundibulum. The maxillary air sinus opens behind the bulla at the posterior end of the hiatus semilunaris.

Inferior Meatus

It is present deep into the inferior concha and receives the opening of the nasolacrimal duct.

Sphenopalatine Foramen is present behind the superior concha and transmits the sphenopalatine artery and nasal branches of the pterygopalatine ganglion.

Skull Of The Newborn

The size of the cranium (brain box) is larger as compared to the facial skeleton. The brain box (calvaria) is large because of the rapid growth of the cerebrum.

The bones of the vault are ossified in membrane while the bones of the base of the skull are ossified in cartilage.

The size of the face at birth is small due to the following facts:

Norma Frontalis

  • The glabella and superciliary arches are not well developed.
  • The frontal bone is present in two halves, i.e., right and left separated by frontal suture.
  • Small size of mandible and maxilla.
  • Rudimentary maxillary air sinus.
  • Non-eruption of teeth.
  • The small size of the nasal cavity.
  • The germs of developing teeth in the superior alveolar process are near the orbital floor.
  • The paranasal sinuses are rudimentary or absent.
  • The two halves of the mandible are united by the fibrous tissue at symphysis menti. These halves join each other at the end of the first year.

Bones Of The Head And Neck Regions Skull of a newborn as seen from front

The Base Of The Cranium

  • The cranial base is relatively short.
  • Occipital and sphenoid bones are joined with each other by the cartilaginous joint.
  • The squamous, lateral, and basilar parts of the occipital bone are separated from each other.
  • The styloid process is not fused with the temporal bone.
  • The mandibular fossa is flat and its articular tubercle is underdeveloped.
  • The stylomastoid foramen is exposed on the lateral surface.

The Lateral View

  • The mastoid process is absent
  • The tympanic plate is represented by a C-shaped plate.
  • The tympanic membrane is attached obliquely and exposed as the bony part of the external acoustic meatus is yet not developed.
  • The cavities of the internal ear, middle ear, Lateral View Anterior fontanelle mastoid antrum, and three ear ossicles are of adult size at birth. However, the petrous temporal bone is much smaller.
  • The angle of the mandible is obtuse 140 degrees
  • The coronoid process is above the level of the head of the mandible

Norma Verticalis

  • The bones of the vault are ossified in the membrane.
  • The angles of the parietal bones are still membranous. Thus there are six fontanelles at four angles of both the parietal bones.
  • The unpaired median fontanelles are called anterior and posterior fontanelles.
  • Two lateral pairs of fontanelles are sphenoidal and mastoid fontanelle.
  • The anterior fontanelle lies at the junction of sagittal, coronal, and frontal sutures.
  • The posterior fontanelle lies at the junction of sagittal and lambdoid sutures.
  • The sphenoidal and mastoid fontanelles are at the sphenoidal and mastoid angles of the parietal bones.

Anterior Fontanelle

The anterior fontanelle is present at the junction of frontal, coronal, and sagittal sutures hence, diamond-shaped. It measures about 4 cm in anteroposterior and 2.5 cm in transverse dimensions.

Deep to the anterior fontanelle lies superior sagittal sinus. It is usually closed between 18 months and 2 years of age.

Bones Of The Head And Neck Regions Newborn skull as seen from lateral aspect

Bones Of The Head And Neck Regions Newborn skull as seen from above

Bones Of The Head And Neck Regions Posterior Nasal Aperture

Bones Of The Head And Neck Regions Norma Frontalis Norma Verticalis Of Foegtal skull

Clinical Significance

  • The bulging of the fontanelle indicates increased intracranial pressure.
  • The depressed fontanelle indicates dehydration.
  • As the superior sagittal sinus lies just deep to it blood can be withdrawn from the sinus.
  • The intravenous transfusion of fluid or drugs is also possible through the superior sagittal sinus.
  • The CSF can also be withdrawn from the lateral ventricle of the brain. For this a needle is introduced downwards and laterally at the lateral angle of the fontanelle.
  • The fact, that the anterior fontanelle closes by the age of 2 years, is utilized to determine the age of the child.
  • At the time of birth, fontanelle allows some overlap of the bones of the cranial vault. This helps in the reduction in the size of the foetal head during birth.

Hyoid Bone

Hyoid is a U-shaped bone present in the upper part of the neck.

It is not attached to any other bone but hangs at the level of the 3rd cervical vertebra with the help of muscles and ligaments. The hyoid bone consists of a central body and greater and lesser cornua.

Bones Of The Head And Neck Regions The Anterosuperior Aspect Of Hyoid bone

Hyoid Bone Body

The body is rectangular and has an anterior and a posterior surface.

The anterior surface is convex and faces anterosuperiorly. A median ridge divides it into right and left halves. The posterior surface is concave and smooth.

Hyoid Bone Greater Cornua

Each end of the body is continuous posterolaterally as greater cornu. The greater cornu is flattened. It has two surfaces (upper and lower) and two borders (medial and lateral). The posterior end of the greater cornu is enlarged to form a tubercle.

Hyoid Bone Lesser Cornua

The lesser cornua are small conical projections attached to the bone at the junction of the body and greater cornu on each side.

Each cornu projects upwards and laterally. The lesser cornu may form a synovial joint with the greater cornu.

Hyoid Bone Particular Features

Attachments of muscles on the anterosuperior aspect are shown. Attachments of ligaments and membranes.

Bones Of The Head And Neck Regions The Attachments Of Muscles On Hyoid Bone

Bones Of The Head And Neck Regions The Attachments Of Ligamnets And Membrane

Hyoid Bone Ossification

The hyoid bone ossifies in cartilage by six centers. One center appears in each greater cornua at the end of intrauterine life. Soon after birth two centers appear for the body. One center appears in each lesser cornua at puberty.

Cervical Vertebrae

The cervical part of the vertebral column is highly mobile and its curvature is convex anteriorly. It is made up of 7 cervical vertebrae. A cervical vertebra is characteri¬ zed by the presence of a foramen in each transverse process (foramen transversarium). The 1st, 2nd, and 7th vertebrae are atypical, while 3rd to 6th vertebrae are typical.

Typical Cervical Vertebrae

A typical cervical vertebra consists of a body and vertebral arch. The body and vertebral arch enclose a vertebral foramen, which lodges the spinal cord and its meninges.

Cervical Vertebrae Body

  • The body of the cervical vertebra is the smallest among all vertebrae. The shape of the cervical vertebra is oval, its anteroposterior diameter is less than side to side.
  • The superior surface of the body is concave from side to side because of the presence of an upward-projecting lip on either side.
  • The inferior surface is convex from side to side. The anterior border of the inferior surface projects downwards as a lip.
  • The bodies of the adjacent vertebrae are connected by the intervertebral disc and a pair of synovial unconvertebral joints on each side of the disc.
  • The vertebral foramen is large and triangular.

Bones Of The Head And Neck Regions The Superior Aspect Of A Typical Cervical Vertebra

Vertebral Arch

It consists of pedicles, laminae, superior and inferior articular processes, transverse processes, and spine

Pedicles

These are rounded bars that arise from the posterolateral part of the body. They are directed backward and laterally hence, the vertebral foramen is large and triangular.

Lamina

Laminae are thin plates of bone. They are directed backward and medially from pedicles to meet each other in the midline at the base of the spinous process.

Spinous Process

It is short and bifid.

Articular Process

  • The superior and inferior articular processes are present at the junction of pedicles and laminae and form a continuous articular pillar.
  • The superior articular facet faces upwards and backward while the inferior facet faces downwards and forwards.
  • The superior articular process articulates with the inferior articular process of the above vertebra.
  • Between superior and inferior articular facets articular process is in the form of a bar and is known as an articular pillar.
  • Besides bodies, the articular processes (articular pillar) also carry a considerable load on the head and neck.

Transverse Processes

  • These are short and directed laterally. Each transverse process bears a foramen transversarium.
  • Each process presents anterior and posterior roots (anterior and posterior to the foramen), anterior and posterior tubercles (at the lateral end of anterior and posterior roots), and an intertubercular bar (costotransverse bar) which is present lateral to the foramen.
  • The anterior root, anterior tubercle, intertubercular bar and posterior tubercle represent the costal element (element of rib). The posterior root represents the true transverse process.
  • The foramen transversarium of the cervical vertebrae (except C7) transmits the vertebral artery, sympathetic nerve plexus, and vertebral vein.
  • The upper surface of the costotransverse bar is grooved and lodges the ventral ramus of the corresponding cervical nerve.

The First Cervical Vertebra

The first cervical vertebra is also known as the atlas.

It is easily identified from the rest of the other cervical vertebrae because:

  • It is ring-shaped.
  • It has nobody.
  • It is the widest of all other cervical vertebrae.
  • It has no spinous process.

The bone has two large masses (lateral masses) joined anteriorly by a short anterior arch and joined posteriorly by a much longer posterior arch.

The superior surface of each lateral mass bears an elongated kidney-shaped concave articular facet for articulation with the occipital condyle (to form atlanto-occipital joint).

Bones Of The Head And Neck Regions Schematic Diagram Showing The Parts Of Transverve Process

Anatomical Position

Hold the bone in such a way that the concave superior articular surface of the lateral masses faces upwards. The short anterior arch should face anteriorly.

General Features

Lateral Mass

  • Each lateral mass has a superior articular facet and an inferior articular facet. The superior facet is concave and kidney-shaped. The inferior facet is oval and flat.
  • The inferior facet faces downwards and medially and articulates with the superior articular surface of the axis (2nd cervical vertebra) to form the lateral atlantoaxial joint.
  • The medial surface of each lateral mass bears a tubercle for the attachment of the transverse ligament of the atlas.

The Anterior Arch

  • It shows the presence of a small anterior tubercle in the midline.
  • An oval articular facet is present on the posterior surface in the midline. This facet articulates with the dens of the 2nd cervical vertebra to form the median atlantoaxial joint.

The Posterior Arch

  • The posterior arch is much longer than the anterior and bears a posterior tubercle on its posterior surface in the midline. It represents the rudimentary spinous process.
  • There is the presence of a shallow groove on its superior surface posterior to each lateral mass. The groove lodges the vertebral artery and the first cervical spinal nerve.

The Transverse Process

The transverse process projects laterally from the lateral mass. It has foramen transversarium which transmits vertebral artery, vein, and sympathetic nerve.

Particular Features

  • Attachments of ligaments, membranes, and muscles.
  • Relations of blood vessels and nerves are
  • The Second Cervical Vertebra proc.
  • This vertebra is also known as the axis. It can be easily identified from the rest of the vertebrae because of the presence of dens or odontoid processes.
  • The den is a blunt conical tooth-like process that projects superiorly from the body. The spinous process is long, strong, and bifid and projects posteriorly.

Bones Of The Head And Neck Regions Superior aspect of atlas vertebra

Bones Of The Head And Neck Regions Inferior aspect of atlas vertebra

Bones Of The Head And Neck Regions Superior view of typical cervical vertebra

Bones Of The Head And Neck Regions Superior view of 1st cervical vertebra

Bones Of The Head And Neck Regions Superior view of 2nd vertebra

Bones Of The Head And Neck Regions Superior view of 7th cervical vertebra

Bones Of The Head And Neck Regions Attachment of ligaments and membranes On Superior Surface Of Atlas

Bones Of The Head And Neck Regions Nerve and artery in relation to atlas.

Anatomical Position

Hold the bone in such a way that the body of the vertebra lies anteriorly and the odontoid process faces upwards. The bifid spinous process should face posteriorly.

Bones Of The Head And Neck Regions The anterior aspect of axis vertebra

Bones Of The Head And Neck Regions The posterior aspect of axis vertebra

General Features

  • The odontoid process is about 1.5 cm long. Its anterior surface bears a small oval facet for articulation with the anterior arch of the atlas. The posterior surface shows a groove, which lodges the transverse ligament of the atlas.
  • The upper end of the body bears dens, while the lower surface articulates with the third cervical vertebra through the vertebral disc.
  • Superior articular facets are situated lateral to the odontoid process. These are large oval facets, that articulate with the corresponding inferior facets of the atlas vertebra. Each facet is sloping and partly situated on the body and partly on the pedicle.
  • The transverse processes are small and lie lateral to the superior articular facets.
  • The pedicle, lamina, and spine are massive and very strong. The spine is bifid.
  • The inferior articular process is present at the junction of the pedicle and lamina. Its articular facet faces downwards and forwards.

Bones Of The Head And Neck Regions Superior view of 7th cervical vertebra

Seventh Cervical Vertebra

  • This vertebra is easily identified from the other cervical vertebrae due to the presence of a very long, horizontal spinous process, which is not bifid (ends in a single tubercle).
  • As the tip of the spinous process (tubercle) can be easily felt under the skin it is also called vertebra prominence. The transverse processes are large and have prominent posterior tubercles.
  • The foramen transversarium is small because it does not provide passage to the vertebral artery. It transmits to the accessory vertebral vein only.

Bones Of The Abdominal And Pelvic Regions Notes

Bones Of The Abdominal And Pelvic Regions

The bones of the abdominal region consist of five lumbar vertebrae and intervening intervertebral discs. The bones of the pelvic region consist of two hip bones (right and left), a sacrum, and a coccyx.

The right and left hip bones are joined anteriorly at the pubic symphysis and to the sacrum posteriorly to form a bony pelvis.

We shall first study the lumbar vertebrae, sacrum, and coccyx before studying the bony pelvis. Students are advised to review the features of a typical vertebra (as described in Chapter 4), before studying lumbar vertebrae

Lumbar Vertebrae

The lumbar region of the vertebral column consists of five lumbar vertebrae. The upper four vertebrae are typical while the fifth is atypical.

Features Of A Typical Lumbar Vertebra

Body

The bodies of lumbar vertebrae are large and kidney-shaped. The size of the lumbar vertebrae increases from above downwards as they have to bear the increasing weight of the body.

Pedicles

The pedicles are short and strong. They are directed backward and somewhat laterally. The superior vertebral notches are shallow while inferior notches are deep.

Bones Of The Abdominal And Pelvic Regions A Typical Lumbar Vertebra As Seen

Bones Of The Abdominal And Pelvic Regions A Typical Lumbar Vertebra As Seen.2

Lamina

These are broad and short and do not overlap one another as in the case of thoracic vertebrae.

Vertebral Foramen

The vertebral foramen is large and varies in shape, i.e., oval (LI) to triangular (L4).

Read and Learn More Human Osteology Notes

Transverse Processes

These are thin, long, and often have tapering ends. The posteroinferior aspect of the root of each transverse process bears a small projection called an accessory process.

Superior Articular Processes

These are vertical curved processes and bear concave articular facets facing backward and medially. There is the presence of a nonarticular rough projection on the posterior border of the superior articular process called as mammillary process.

Inferior Articular Processes

These are also vertical processes. They bear a convex articular facet, which is directed forward and laterally.

Spinous Process

The spinous process of a typical vertebra is large, thick, horizontal, and quadrilateral in shape. It presents thickened posterior and inferior borders.

Features of Fifth Lumbar Vertebra

  • The fifth lumbar vertebra is the largest of all the vertebrae. The body and transverse processes of L5 are very massive as they carry the weight of the whole upper body.

Bones Of The Abdominal And Pelvic Regions Superior View Of Fifth Lumbar Vertebra

  • The vertical height of the anterior surface of the body is higher as compared of the posterior surface.
  • This fact is responsible for a prominent sacrovertebral angle (angle between the long axis of the lumbar column and the long axis of the sacrum).
  • The transverse processes of L5 are very large and thick. They have a wide origin, i.e., they arise from the lateral aspect of the pedicle and also encroach on the side of the body.
  • The transverse processes of L5 are massive because they are involved in the transmission of load from the body of L5 to the ilium (through the ilio-lumbar ligament) and to the sacrum (through the lumbo-sacral ligament).
  • The spinous process of the L5 vertebra is short and directed backward and somewhat downwards.
  • The distance between two superior articular processes is almost equal to the distance between two inferior articular processes.
  • (In the case of a typical lumbar vertebra the distance between two superior articular processes is more as compared to the distance between two inferior processes.

Bones Of The Abdominal And Pelvic Regions Superior Aspect Of 5th Lumbar Vertebra

Bones Of The Abdominal And Pelvic Regions Right Lateral View Of A Typical Lumbar Vertebra

Bones Of The Abdominal And Pelvic Regions Superior Aspect Of 5th Lumbar Vertebra

Bones Of The Abdominal And Pelvic Regions Posterior Aspect Of The 5th Lumbar Vertebra

Bones Of The Abdominal And Pelvic Regions Distance Between Two Superior And Two Inferior Articular Processes

Clinical application

Lumbar Spinal Stenosis

  • In this condition, there occurs the narrowing of the lumbar part of the vertebral canal.
  • The condition may result due to bulging (prolapse) of the intervertebral disc, arthritic proliferation, or ligamentous degeneration.
  • Sometimes stenosis may be congenital also. The stenosis causes compression of the spinal nerve roots of the cauda equina.
  • The condition is usually treated surgically by laminectomy (excision of vertebral laminae) or by removing the entire vertebral arch.

Low Back Pain

  • The neural arch at L4 and L5 levels is involved in the transmission of a considerable magnitude of load. This fact indicates that the joints between the articular facets may be the site for low back pain.
  • Probably, the pain is due to stretching of the joint capsule (or transmission of load across it), which contains a nociceptive type IV receptor system (Pal and Routal, 1987).

Instability of Spine Following Laminectomy

About 20% of the load in the lumbar region passes through the laminae of lumbar vertebrae. Thus the laminectomy leads to instability of the lumbar column. Pal and Routal (1987) strongly recommended the preservation of the integrity of the articular facet joints in laminectomy.

Prolapsed or Herniated Disc

A prolapsed disc occurs when the nucleus pulposus pushes outward, distorting the shape of the disc.

If the annulus fibrosus of the disc ruptures (usually on the posterolateral aspect and most commonly at L4/L5 or L5/S1 levels) then the nucleus pulposus is herniated through the rupture.

Both in prolapsed or herniated disc surrounding tissue become inflamed and swollen. The tissue of the disc may press on the nerve or spinal cord, causing pain e.g. sciatica.

The Sacrum

The sacrum is composed of five fused sacral vertebrae in adults. It is a large, triangular wedge-shaped bone.

It is wedged between two hip bones and forms the posterior part of the bony pelvis. It transmits the weight of the upper body received through L5 to the pelvic girdle through sacroiliac joints.

The sacrum is triangular because there is a portion below the sacroiliac joint) is not involved in weight bearing hence its size diminishes rapidly.

The triangular sacrum presents an upper end or base. The base is formed by the superior surface of the SI vertebra.

Bones Of The Abdominal And Pelvic Regions The Anterior (Pelvic) Surface Of Sacrum

It articulates with the fifth lumbar vertebra at the lumbosacral joint. The lower end of the sacrum is tapering also known as apex. It articulates with the coccyx.

The sacrum presents an anterior (or pelvic) concave surface and a dorsal (or posterior) convex surface. The pelvic surface shows the presence of four pairs of anterior sacral foramina.

Similarly, the posterior surface also shows four pairs of posterior sacral foramina the sacrum also presents the right and left lateral sacrum also presents the right and left lateral of the right and left hip bones to form sacroiliac joints The Mcra( cam, the continuation of the vertebral canal in the sacrum The canal Bes posterior to the median part of the sacrum formed by fused bodies.

The sacral canal communicates with the anterior and posterior sacral foramina through which passes the ventral and dorsal rami of sacral nerves.

Bones Of The Abdominal And Pelvic Regions The Superior base of Sacrum

Anatomical Position

Hold the bone in such a way that the pelvic (anterior) surface is directed forward and downwards. In this situation, the base of the sacrum will look forward and upwards.

Bones Of The Abdominal And Pelvic Regions The Posterior Surface Of Sacrum

General Features

The base of the Sacrum

It is formed by the upper surface of the first sacral vertebra. The base consists of a centrally placed oval body and the upper surface of the right and left ala (lateral mass) on each side of the body.

Posterior to the body there is the presence of a triangular sacral canal bounded by thick pedicles and laminae.

The superior articular facets project upwards from the junction of the pedicles and laminae.

The superior articular facets of the sacrum articulate with the inferior articular facets of the 5th lumbar vertebra.

Posteriorly, there is a resence of a tubercle at the meeting point of two laminae. This tubercle represents the rudimentary spinous process.

The body of the first sacral vertebra is large and much wider. Its anterior border is projecting and called the sacral promontory The lateral portion of the base (ala of the sacrum) is smooth and like a wing.

The ala of the sacrum is strong as it has to transmit the load from the lumbosacral joint to the sacroiliac joint.

Pelvic (Anterior) Surface

This surface is smooth, concave, and faces downwards and forwards. This surface presents four transverse lines indicating the site of fusion of 5 sacral vertebrae.

At the ends of these transverse lines, there are four pairs of sacral foramina on this surface. These foramina communicate with the sacral canal through intervertebral foramina.

Posterior (Dorsal) Surface

The dorsal surface of the sacrum is rough and convex.

  • In the midline, there is the presence of a longitudinal ridge called as median sacral crest, which is formed by the fused spinous processes of the upper four sacral vertebrae The dorsal surface presents four pairs of dorsal sacral foramina, which communicate with the sacral canal and transmit dorsal rami of upper four sacral spinous nerves.
  • An area between the right and left foramina is formed by the fusion of laminae of the upper four sacral vertebrae.
  • The laminae Body of S1 of the fifth sacral vertebra (and sometimes the fourth also) fails to fuse in the midline and presents an inverted U or V-shaped gap called a sacral hiatus.
  • On either side of the sacral hiatus are the sacral cornua, which represent the inferior articular processes of the fifth sacral vertebra.
  • The sacral hiatus contains fatty connective tissue, filum-terminale, the S5 nerve and the coccygeal nerve. The sacral cornua can be easily palpated in a living person and are useful guide to locate the hiatus for the injection of anesthetic agents.
  • On the medial side of dorsal sacral foramina is a vertical crest consisting of four small tubercles. These tubercles represent the fused articular processes of fused sacral vertebrae. This crest is called intermediate crest.
  • On the lateral side of the dorsal sacral foramina there is the presence of lateral sacral crest. This crest is formed by the fusion of transverse processes.

Lateral Surface of the Sacrum

On both the lateral surfaces of the sacrum, there is the presence of a large ear-shaped auricular surface that articulates with the ilium of each hip bone to form a sacroiliac joint.

Posterior to the auricular surface is a rough area, the sacral tuberosity for attachment of strong interosseous sacroiliac ligament.

Apex of the Sacrum

It has an oval facet for articulation with the coccyx.

The Coccyx

It is a small triangular bone formed by the fusion of four rudimentary vertebrae. It has an upper end (base), lower end, and pelvic and dorsal surfaces.

The base is formed by the first coccygeal vertebra, which has an oval facet for articulation with the apex of the sacrum.

Bones Of The Abdominal And Pelvic Regions Lateral Surface Of Sacrum

Bones Of The Abdominal And Pelvic Regions The Coccyx Bone As Seen From Dorsal Aspect

  • The first coccygeal vertebra also has transverse processes and cornua.
  • The cornua project upwards from the base of the coccyx and are connected with the cornua of the sacrum through ligaments.
  • The remaining coccygeal vertebrae are featureless and represented by the nodules of bone.

Bones Of The Abdominal And Pelvic Regions Anterior surface of sacrum

Bones Of The Abdominal And Pelvic Regions Posterior aspect of sacrum

Particular Features of the Sacrum and Coccyx

Attachments of the Muscles on the Sacrum and Coccyx

  • lilacs and piriformis muscles are attached on the pelvic surface of the sacrum.
  • The coccygeus muscle is inserted on the pelvic surface of the 5th sacral vertebra and coccyx.
  • The levator ani is inserted on the tip of the coccyx.
  • Note the origin of gluteus maximus from the sacrum and coccyx from their dorsal surfaces.
  • The dorsal surface also gives origin to the erector spinae and multifidus.

Attachment of Ligaments

  • The sacrotuberous ligament is attached to the lower part of the dorsal surface of the sacrum.
  • The lateral margin of the lower part of the sacrum and the lateral margin of the coccyx gives attachment to the sacrospinous ligament.
  • The interosseous ligament of the sacrospin¬ ous joint is attached to the rough area on the lateral surface posterior to the auricular surface.
  • The iliolumbar ligament is attached to the lateral margin of the ala and iliac crest.
  • Nerves and Blood Vessels about the Pelvic and Dorsal Surface of the Sacrum
  • The median sacral artery is related to the midline.

Bones Of The Abdominal And Pelvic Regions The pelvic surface of sacrum showing the particular features

Bones Of The Abdominal And Pelvic Regions The dorsal surface of sacrum showing the particular features

Bones Of The Abdominal And Pelvic Regions Attachment of ligaments

  • The lateral sacral artery is related lateral to the ventral sacral foramina.
  • The right and left sympathetic trunks are related medial to the ventral sacral foramina.
  • The superior rectal artery is related to the left side of the midline.
  • The dorsal and ventral sacral foramina give passage to the dorsal and ventral spinal rami respectively.
  • The sacral canal contains the cauda equina.
  • The subdural and subarachnoid spaces end at the middle of the sacrum.
  • Each ala of the sacrum is related to the following structures medial to the lateral-sympathetic trunk, lumbosacral trunk, iliolumbar artery, and obturator nerve.

Clinical Importance

Caudal Epidural Anesthesia

As the subdural and subarachnoid spaces end at the level of the middle of the sacrum, the sacral canal contains extradural or epidural space filled with fibro-fatty tissue. In this space, there are spinal nerves of cauda equina covered by dura.

In epidural anesthesia (caudal analgesia) a local anesthetic agent is injected in the sacral canal through the sacral hiatus. The sacral hiatus is located by palpating the sacral cornua and lower end of the median sacral crest.

The anesthetic agent when injected in the sacral hiatus acts on the spinal nerves in the cauda equina (usually S2 to coccygeal nerves).

This procedure is usually used to relax the perineal musculature for painless childbirth.

Abnormal Fusion of Lumbar and Sacral Vertebrae Sometimes (in about 5% of people) L5 vertebra is partly or completely fused with the sacrum.

The condition is called sacralization of the L5 vertebra. In some cases, the S1 vertebra is separated from the sacrum and may be partly or completely separated from the sacrum.

This condition is called lumbarization of the S1 vertebra. Both the above conditions may produce painful symptoms in persons having abnormal fusion of the vertebra.

Bony Pelvis

The bones of the pelvic region consist of two hip bones (right and left), a sacrum, and a coccyx. The right and left hip bones are joined anteriorly at the pubic symphysis and to the sacrum and coccyx posteriorly to form a pelvic girdle or bony pelvis.

Above it articulates with the lumbar part of the vertebral column at the lumbosacral joint. Below it is attached to the lower limbs (femora) at hip joints.

Bones Of The Abdominal And Pelvic Regions The Bony Pelvis male Female

Bones Of The Abdominal And Pelvic Regions The Bony Pelvis male Female.2

Bones Of The Abdominal And Pelvic Regions Anterior Aspect Of The Female Pelvis.

Bones Of The Abdominal And Pelvic Regions Superior Aspect Of The Female Pelvis

Functions of the Bony Pelvis

  • The bony pelvis is the basin-shaped ring of bones, which protects the distal part of the intestine, urinary bladder, and internal genital organs.
  • The main function of the bony pelvis is to transmit the weight of the upper body from the vertebral column to the lower limbs.
  • It transmits the thrust between the vertebral column and lower limbs.
  • Provides attachment to the powerful muscles.
  • It gives passage to the fetus at the time of birth.

The bony pelvis is divided into greater and lesser pelvis. The greater pelvis is also called a false pelvis.

The lesser pelvis is called as true pelvis. The greater and lesser pelves are separated from each other by an imaginary plane, i.e., the plane of the pelvic inlet or pelvic brim).

Bones Of The Abdominal And Pelvic Regions Diagrammatic Representation Of The Coronal Section Of Pelvis

Bones Of The Abdominal And Pelvic Regions Diagrammatic Represenation Of The Sagittal Section Of Male Pelvis

Greater Pelvis

The walls of the greater or false pelvis are formed by the iliac fossa of the hip bones and posteriorly by the ala of the sacrum. Anteriorly, the greater pelvis presents no bony wall.

Lesser Pelvis

The lesser or true pelvis presents an inlet (superior pelvic aperture), a pelvic cavity, and an outlet (inferior pelvic aperture). The Pelvic Inlet The plane of the pelvic inlet slopes obliquely downwards and forward.

The axis of the inlet is determined by a line drawn perpendicular through the center of the plane. The plane of the pelvic inlet makes an angle of 50 to 60 with the horizontal plane.

The boundary of the pelvic inlet on each side is formed behind by the sacral promontory, the anterior margin of the ala of the sacrum, the linea terminalis, and the upper end of the symphysis pubis.

(The linea terminalis of each hip bone consists of an arcuate line of ilium iliopubic eminence, pectin pubis, and pubic crest).

The Cavity of the Lesser Pelvis

The cavity of the lesser pelvis extends downwards and backward from the pelvic inlet and lies between the inlet and outlet. Anteriorly, the cavity is bounded by the symphysis, the body of the pubis, and two rami of the pubis.

On each side, the wall is formed by ilium and ischium below the arcuate line. Posteriorly it is limited by the concave pelvic surface of the sacrum and coccyx. The posterior wall of the cavity is much longer than the anterior wall.

The Outer or Inferior Pelvic Aperture (Pelvic Outlet)

It is bounded anteriorly by the lower margin of the symphysis pubis, anterolaterally by the conjoined ischiopubic rami, laterally by the ischial tuberosities, posterolaterally by sacrotuberous ligaments, and posteriorly by the tip of the coccyx.

Thus the lower pelvic aperture is somewhat diamond-shaped. The plane of the pelvic outlet lies between the lower border of the symphysis pubis and the tip of the coccyx.

A line drawn perpendicular to the center of this plane is known axis of the pelvic outlet. The plane of the pelvic outlet makes an angle of 10 to 15 with the horizontal plane.

Bones Of The Abdominal And Pelvic Regions Various Diameters Of Pelvic Outlet

The Axis of Pelvic Cavity

The axis of the pelvic cavity is an imaginary axis passing through the pelvic cavity between the inlet and outlet of the pelvic cavity the axis is concave anteriorly and passes parallel to the sacrococcygeal curve.

The axis of the pelvic cavity is important because this axis passes the head of the fetus during childbirth. Hence, the axis of the pelvic cavity is also called as axis of the birth canal.

Bones Of The Abdominal And Pelvic Regions The Axis Of The Pelvic Cavity

Bones Of The Abdominal And Pelvic Regions Various Diameter Of Inlet Of Pelvis

Bones Of The Abdominal And Pelvic Regions Differences Between Male And Female Pelves

Diameters of the Pelvi

The diameter of the pelvic inlet and outlet are important in females due to childbearing

Measurements of the Inlet in Adult Females

Anteroposterior diameter: It extends between the middle of the sacral promontory to the upper margin of the symphysis pubis. It measures about 105 to 110 mm.

The transverse diameter: Is the widest measurement across the inlet. It measures about 125 to 130 mm.

The oblique diameter: It is measured from the sacroiliac joint of one side to the iliopubic eminence of the other side. It measures about 120 to 125 mm.

Measurements of the Outlets in Adult Females The anteroposterior diameter: Is measured from the lower border of the symphysis pubis to the tip of the coccyx. It is about 125 mm.

The transverse diameter: It is the distance between two ischial tuberosities. It measures about 110 to 118 mm. The oblique diameter: It is the distance between the junction of the ischiopubic ramus of one side and the midpoint of the sacrotuberous ligament of the opposite side.

Bones Of The Abdominal And Pelvic Regions Various Diameter Of Inlet Of Pelvis

Anatomical Position of the Pelvis

Hold the articulated pelvis in such a way that the upper end of the pubic symphysis and the anterior superior iliac spines lie in the same vertical plane (place these points against a wall)

In this position, the tip of the coccyx lies almost at the level of the upper margin of the symphysis pubis.

The pelvic inlet faces forward and upwards and the pelvic outlet faces downwards and backwards.

In this position sacrum faces downwards and forwards.

Differences Between Male and Female Pelves

The pelves of males and females differ significantly. These differences are due to childbearing function in females. For identification of sex from human skeletal remains, the pelvis or even a single hip bone is the most useful because here the sexual differences are clearly defined.

Bones Of The Abdominal And Pelvic Regions The Sub-Pubic Angle In Male Is 50 to 60 and in female and 90

Bones Of The Thoracic Region Notes

Bones of the Thoracic Region

The skeleton of the thoracic region forms a bony cage, which protects the lungs, heart, and some upper abdominal organs.

This cage is formed by the following bones and cartilages:

  1. Thoracic vertebrae and intervertebral discs.
  2. Ribs and costal cartilages.
  3. The sternum.

The thoracic cage is narrower at its superior end and broader at its inferior end. The cage is flattened anteroposteriorly.

Posteriorly, it is formed by 12 thoracic vertebrae and intervertebral discs. The sidewalls of this cage are made up of 12 ribs on each side.

The posterior end of each arched rib articulates with the vertebral column.

Manubriosternal Angle

The anterior end of each rib is attached to the costal cartilage. Through these costal cartilages, ribs gain attachment to the sternum.

The sternum is a flat narrow bone situated on the anterior aspect of the thoracic cage.

Bones Of The Thoracic Region The thoracic cage as seen from anterior aspect

Bones Of The Thoracic Region Vertebra, ribs, costal cartilages and sternum forming the thoracic cage

Sternum

The sternum is a flat, elongated bone measuring about 6 inches in length. It is situated anteriorly in the wall of the thorax.

From above downwards, the sternum consists of three portions, i.e., the manubrium, the body, and the xiphoid process.

The body is the middle and largest portion of the sternum. The junction of the manubrium and the upper end of the body forms the manubriosternal joint (the sternal angle).

The junction of the lower end of the body and the xiphoid process forms the xiphisternal joint.

The upper border of the manubrium is concave. It is known as a suprasternal notch.

Manubriosternal Angle

Lateral to the suprasternal notch are clavicular notches that articulate with the medial ends of the clavicles to form sternoclavicular joints.

Read and Learn More Human Osteology Notes

Inferolateral to the clavicular notch there lies a costal notch where the first costal cartilage articulates with the manubrium to form a sternocostal joint. This joint is classified as synchondrosis (primary cartilaginous joint).

The manubrium and the body of the sternum lie in different planes at the manubriosternal joint, therefore the joint projects forwards. This projecting angle is called as angle of Louis or sternal angle.

Bones Of The Thoracic Region Parts of sternum as seen from front

General Features Manubrium

  • The manubrium is the widest and thickest of the three parts of the sternum.
  • It is roughly quadrilateral in shape At the sternal angle, the second costal cartilage articulates with the lower end of the manubrium and the upper end of the body.
  • As the sternal angle is projecting and subcutaneous it is an easily palpable landmark. This fact is utilized to count the ribs. The rib counting starts with the 2nd rib adjacent to the sternal angle.
  • The lower end of the manubrium lies at the level of the lower border of the T4 vertebra.

Bones Of The Thoracic Region The lateral view of sternum

Body of the Sternum

The body of the sternum is a long and thin plate of bone. Its lateral borders present costal notches for articulation with 2nd to 7th costal cartilages.

All these joints are synovial. In adults, the body of the sternum is made up of four pieces (sternebrae).

These pieces of bones are joined to each other by primary cartilaginous joints. These joints begin to fuse soon after puberty. In an adult, these fusion sites are seen as three transverse ridges.

Xiphoid Process

The xiphoid process is the smallest, triangular part of the sternum. The upper end of the xiphoid process meets the body of the. sternum to form xiphisternal joint.

The lateral border of the xiphoid process has a demi facet for articulation with the 7th costal cartilage.

The xiphoid process is cartilaginous in young people. It begins to ossify at about the third year of age.

Manubriosternal Angle

It gets completely ossified at about 40 years of age. It fuses with the body of the sternum in old people.

Sternum Particular Features

Attachments of Muscles on the Anterior Surface of the Sternum Note the origin of the sternal head of the sternocleidomastoid and pectoralis major muscles and insertion of rectus abdominis with the help.

Muscles attached on the posterior aspect of the sternum. Note the origin of sternohyoid, sternothyroid, and sternocostalis with the help. Also, note the reflection of the pleura on both the sides of sternum.

Sternum Ossification

The sternum develops by the fusion of the right and left cartilaginous plates in the midline. After the fusion, many centers of ossification appear in the cartilaginous model.

Sternum Clinical importance

Fractures

Sternal fractures may occur due to automobile accidents. The sternum is broken into pieces due to crush injuries against the steering wheel.

Bones Of The Thoracic Region The Origin Of Muscles From Anterior Aspect Of Sternum

Bones Of The Thoracic Note The Attachment Of Muscleus And Relation Of Pleura On the Posterior Aspect Of Sternum

Bones Of The Thoracic Region The Ossifications Of Sternum

Sternotomy

For coronary bypass surgery and surgeries on lung, these organs are exposed by cutting the sternum in the midline. A wide gap is exposed between two split parts of the sternum because of the elasticity of the costal cartilage and the flexibility of the ribs. After surgery two splitted parts of the sternum are joined by wire sutures.

Bone marrow biopsy

As the sternum is superficial (subcutaneous) it is best suited for needle biopsy of bone marrow. The bone marrow sample is obtained from the spongy bone of the sternum with the help of a needle. A bone marrow biopsy is needed to diagnose blood abnormalities and for bone marrow transplantation.

Sternum is helpful in the identification of sex To a certain extent the sex of an individual can be identified with the help of the sternum as the female sternum is short and wide as compared to males, Jit, et al. (1980). The determination of the sex of bones is needed in medico-legal cases.

Manubriosternal Angle

Congenital defects of sternum As the sternum develops by the fusion of two halves of the sternum in the midline, if these two pieces fail to fuse then the heart is exposed on the thoracic wall (ectopia cordis).

In this condition, pericardium also fails to form. Sometimes there may be the presence of a foramen in the body of the sternum. This occurs due to faulty ossification.

Ribs

Ribs are curved, flat bones that form the greater part of the thoracic wall.

They are arranged in twelve pairs. The length of the ribs increases from the first to the seventh rib. Thereafter the length gradually decreases from the eighth to the twelfth rib.

Each rib articulates posteriorly with the corresponding vertebra. The anterior ends of ribs (except the eleventh and twelfth ribs) articulate with the sternum through costal cartilages.

Bones Of The Thoracic Region Thoracic Cage As Seen From Anterior Aspect

Bones Of The Thoracic Region Inferior Aspect Of The Right Typical Rib

Classification of Ribs

There are three types of ribs:

True Ribs

These ribs are directly attached to the sternum through their costal cartilage. The first seven ribs are true ribs and these ribs are also called vertebrosternal ribs.

False Ribs

These ribs are indirectly connected to the sternum. Their costal cartilages are joined to the costal cartilages of superior ribs. The eighth to the tenth ribs are false ribs and are also called vertebrochondral ribs.

Floating Ribs

The eleventh and twelfth ribs are not connected with the sternum. Their anterior ends are free and covered by rudimentary costal cartilage. They are also known as vertebral ribs or floating ribs.

Ribs may also be classified as typical and atypical ribs. The typical ribs are those, that have the same (common) features. The 3rd to the 9th ribs are typical ribs.

Manubriosternal Angle

The atypical ribs have special features therefore can be differentiated from the rest of the ribs. The atypical ribs are 1st, 2nd, 10th, 11th and 12th ribs.

Bones Of The Thoracic Region True False And Floating Ribs

The Typical Ribs

A typical rib consists of a head, neck, tubercle, angle, and shaft. The head is present at the posterior end and bears one or two articular facets.

The tubercle is a knob-like structure present at the junction of the neck and shaft.

The shaft is long and curved. The convex surface is the external surface while the concave surface is the internal surface, which bears a groove called a subcostal groove.

The upper border of the shaft is rounded while the lower border is sharp. The sternal end bears a concave depression for attachment of costal cartilage.

Bones Of The Thoracic Region Typical rib as seen from posterior aspect

Bones Of The Thoracic Region Typical Rib As Seen From Inferior Aspect

Ribs Side Determination

  • The end of the rib having the head, neck, and tubercle (posterior end) should be kept posteriorly.
  • The concave curved surface should be kept medially.
  • The sharp border (inferior border) of the shaft should be kept downwards.

Thoracic Cage Bones

Ribs Anatomical Position

  • The posterior end should be kept near the midline.
  • The posterior end is at a higher level as compared to the anterior end.

Ribs General Features

The Posterior or Vertebral End

It includes the head, neck, and tubercle.

  • The head presents two articular facets separated by the crest of the head. The lower facet is large and articulates with the body of the numerically corresponding vertebra.
  • The upper small articular facet articulates with the body of the adjacent upper vertebra. The crest of the head is connected to the intervertebral disc by intra-articular ligament.
  • The neck is short and has a sharp upper border. It is sometimes called as crest of the neck. The neck has an anterior smooth and a posterior rough surface.
  • On the posterior aspect of the rib, just lateral to the neck, there is the presence of an elevation called a tubercle. The tubercle has a medial articular (smooth) and lateral non-articular (rough) part.

The Anterior End

The anterior end of the rib has a cup-shaped depression for articulation with the lateral end of the corresponding costal (smooth) cartilage to form a costochondral joint.

The Shaft

The shaft of a typical rib is thin, flat, and curved. It forms the major part of the rib. It
extends between the tubercle and the anterior end of the rib.

  • It has a superior rounded border and a sharp inferior border. It has an outer convex and an inner concave surface The inner surface shows a shallow costal groove just above the inferior border.
  • The costal groove is well-defined in the middle part of the shaft.
  • A short distance lateral to the tubercle rib bends anteriorly. This is called as posterior angle.
  • The rib also shows a twisting, because of which, two ends of the rib cannot touch a horizontal plane simultaneously (when kept on the table.

Bones Of The Thoracic Region Cross section Passing Through Shaft Of A Typical Rib

Ribs Particular Features

Thoracic Cage Bones

Joints about the Typical Rib

  • The head of a typical rib articulates with the adjacent vertebral bodies (with the numerically corresponding body and a body above it) and intervertebral disc to form a costovertebral joint.
  • The costotransverse joint is formed between the costal facet of the transverse process and the articular part of the tubercle.
  • This joint is supported by various costotransverse ligaments, i.e., the lateral costotransverse, superior costotransverse, and costotransverse ligaments.

Bones Of The Thoracic Region Cross section Passing Through Shaft Of A Typical Rib

Bones Of The Thoracic Region The Costotransverse And Costoverterbral Joints

The Muscles Attached to the Rib

The attachments of external intercostal, The various muscles are also attached on the external surface of the ribs, i.e., pectoralis minor, serratus anterior, latissimus torsi, and back muscles.

The parietal pleura is related to the inner surface of the rib.

Bones Of The Thoracic Region The Attachment Of muscles Between Two Adjancent Ribs.

Nerves and Vessels Related to the Typical Rib

  • The sympathetic trunk descends downwards on the anterior aspect of the heads of the typical ribs.
  • The intercostal nerve and vessels lie in the costal groove between the internal intercostals and innermost intercostal muscles.

The Atypical Ribs

The First Rib

The first rib is the shortest, broadest, curved, and flat rib. As compared to the typical ribs its head has only one articular facet for the body of the first thoracic vertebra.

The posterior angle of the rib lies at the tubercle itself. The shaft shows inner and outer borders thus superior and inferior surfaces.

Bones Of The Thoracic Region First Rib As Seen From Superior Aspect

(This is in contrast to the typical ribs, which show superior and inferior borders and outer and inner surfaces.)

The superior surface of the first rib is rough and shows the presence of two grooves. The inferior surface is smooth and there is the absence of a subcostal groove.

First Rib Side Determination

  • The head, neck, and tubercle are located posteriorly near the midline.
  • The broad anterior end lies anteriorly.
  • The concave inner border lies medially.
  • The rough superior surface of the shaft (having grooves) should face superiorly.

Thoracic Cage Bones

First Rib Anatomical Position

  • Keep the posterior or vertebral end near the midline.
  • The anterior end is at the lower level as compared to the posterior end. In this position, the upper surface should face anterosuperiorly.

First Rib General Features

First Rib The Posterior End

  • The posterior end consists of the head, neck, and tubercle. The head is rounded, small, and bears only one circular articular facet.
  • The neck is rounded and extends upwards and posterolaterally.
  • The neck shows superior, posterior, inferior, and anterior surfaces.
  • The tubercle is large and prominent. The oval articular facet on the tubercle articulates with the transverse process of a first thoracic vertebra.

The Shaft

  • The shaft is flat and shows superior and inferior surfaces and outer and inner borders.
  • The superior surface of the first rib shows two shallow but wide grooves separated by a faint ridge. This ridge is continuous medially with the scalene tubercle on the inner border.
  • The inferior surface is smooth and related to the parietal (costal) pleura.

Particular Features

Attachments of the Muscles on the First Rib

  • The subclavius muscle arises from the superior surface near its anterior end.
  • The scalenus anterior is inserted on the scalene tubercle. The scalenus medius is attached behind the groove for the subclavian artery.
  • The intercostal muscles arise from its outer border.
  • The first digitation of the serratus anterior arises from its outer border

Relations of the Nerves, Vessels and Ligaments

  • The costoclavicular ligament is attached on its superior surface near its anterior end The inner border gives attachment to the suprapleural membrane.
  • The groove anterior to the scalene tubercle lodges the subclavian vein.
  • The groove posterior to the scalene tubercle lodges the subclavian artery and lover trunk of the brachial plexus.
  • The anterior surface of the neck is related from the medial to lateral side to the sympathetic trunk, first posterior intercostal vein, superior intercostal artery, and ascending branch ofthe ventral ramus of the first thoracic nerve.

The Second Rib

  • The second rib is almost twice the length of the first rib. The shaft has an external surface directed laterally and slightly upwards.
  • This surface presents a prominent rough area near the middle of the shaft.
  • It has a faint, short costal groove in the posterior part of the internal surface, which is directed downwards and medially.

Thoracic Cage Bones

Second Rib Particular Features

  • The prominent rough area on the outer surface, just behind the middle of the shaft, gives origin to the 1st and 2nd digitations of the serratus anterior.
  • The outer surface in its posterior part gives insertion to the scalenus posterior muscle.
  • The intercostal muscles are attached to its upper and lower borders.

Bones Of The Thoracic Region Particular Features Of The First Rib

Bones Of The Thoracic Region Medical End And Inferior Aspect Of Right Typical Rib

Bones Of The Thoracic Region Superior Surface Of Right First Rib

Bones Of The Thoracic Region The General Features Of 2nd Rib

Bones Of The Thoracic Region The Second Rib Showing Attachment Of Muscles

The Tenth Rib

It also presents the head, neck, tubercle, posterior angle, and shaft, like a typical rib.

However, it differs from typical ribs because it presents a single articular facet on its head for articulation with the 10th thoracic vertebral body.

The Eleventh Rib

This rib is short as compared to the tenth rib. It has no neck or tubercle.

Its lateral end is tapering while the vertebral end bears a single articular facet for the body of the eleventh thoracic vertebra.

Thoracic Cage Bones

The Twelfth Rib

  • The twelfth rib is shorter than the eleventh.
  • It is directed downwards, laterally, and forwards.
  • Similar to the eleventh rib it has no neck or tubercle.
  • It has no angle and there is also the absence of a subcostal groove.
  • It has a single facet on the head for articulation with the body of the 12th thoracic vertebra.
  • It has a pointed lateral end, which gives attachment to cartilage.
  • This rib presents upper and lower borders and anterior and posterior surfaces.

Bones Of The Thoracic Region The General Features of 12th rib Anterior Aspect

Bones Of The Thoracic Region Posterior Aspect

  • The anterior surface is smooth and concave and faces slightly upwards.

Particular Features of the 12th Rib

  • The medial part of the upper border gives attachment to the intercostal muscles.
  • The lateral part of the upper border gives attachment to the diaphragm.
  • The quadratus lumborum muscle with its covering (anterior layer of the thoraco¬ lumbar fascia) is attached to the medial half of the anterior surface.
  • The transverse abdominis muscle is attached to the lower lateral part of the anterior surface.

Bones Of The Thoracic Region Ossifivation Of Typical Rib

Bones Of The Thoracic Region Ossifivation Of Typical Rib.2

  • The lower limit of the parietal (costal) pleura crosses the anterior surface of the rib and quadratus lumborum muscle. Thus costodiaphragmatic recess extends on the anterior aspect of the medial half of the rib.
  • The attachments of the muscles on the posterior aspect of the twelfth rib.

Ossification of Rib

A typical rib is ossified from one primary and three secondary centers (one for the head and two for the tubercle). Primary and secondary centers fuse after 20 years of age.

The Costal Cartilages

  • The costal cartilages are flattened bars of hyaline cartilage.
  • They prolong the ribs anteriorly.
  • Each costal cartilage has anterior and posterior surfaces and upper and lower borders.

Bones Of The Thoracic Region Ossification Of A Typical RIb

  • The first seven costal cartilages join to the sternum.
  • The 8th, 9th, and 10th articulate with the cartilage just superior to them. The 11th and 12th costal cartilages form caps on the anterior end of these ribs.
  • The length of the costal cartilage increases from the first to the seventh. The length decreases gradually from the 8th to the 12th.
  • The costal cartilage provides elasticity and mobility to the thoracic wall.
  • They prevent fractures of the sternum and ribs due to their resilience.

Costal Cartilages Clinical Importance

Fractures of Ribs

  • When there occurs a direct injury on the sidewall of the chest, the broken ends of the ribs may tear the pleura and lung. This may lead to the collection of air (pneumothorax) or blood (haemothorax) in the pleural cavity.
  • When there is indirect violence, due to compression of the chest against the steering wheel in accidents, ribs are commonly fractured near their angles.
  • Ribs are Used for Bone Grafting Similar to the fibula ribs are also used for bone grafting. In this procedure, the periosteum of the rib is incised along its length and a segment of the rib is removed for grafting leaving the periosteum intact. After some time, rib regenerates deep to the periosteum.

Extra Ribs

  • Sometimes the number of ribs may increase (than normal 12 pairs) due to the presence of a cervical or lumbar rib. The cervical rib articulates with the 7th cervical vertebra but usually fails to attach to the sternum.
  • The anterior end of the cervical rib may attach to the first rib. The cervical rib may compress the lower trunk of the brachial plexus.
  • This may lead to pain and numbness in the shoulder and upper limb.
  • This rib may also compress the subclavian artery resulting in pain in the upper limb due to poor blood supply to the limb muscles. Lumbar ribs are less common as compared to the cervical ribs.

Thoracic Vertebrae

The thoracic part of the vertebral column is formed by the twelve thoracic vertebrae and intervertebral discs. This part of the column is concave anteriorly.

Thoracic vertebrae are larger and stronger than cervical vertebrae.

Compared to the cervical vertebrae they also have longer and larger transverse processes. The following three special features are helpful in the identification of thoracic vertebrae.

  • Presence of costal facets or demi-facets on the bodies for articulation with the heads of the ribs.
  • Presence of costal facets on their transverse processes for articulation with the tubercle of the ribs (except for Til and T12 vertebrae).
  • The spinous processes of T3 to T9 vertebrae are long and slope downwards.
  • The spinous process of Til and T12 are shorter, broader, and directed more posteriorly.
  • The 2nd to 9th thoracic vertebrae are typical because they bear common bony features. The 1st, 10th 11th, and 12th thoracic vertebrae are atypical.

Bones Of The Thoracic Region Superior Surface Of Right Second Rib

Bones Of The Thoracic Region Left Lateral Veiw Of A Typical Thoracic Vertebra

 

Bones Of The Thoracic Region Superior Aspect Of A Typical Thoracic Vertebra

Bones Of The Thoracic Region Superior Aspect Of 12th thoracic Vertebra

Typical Thoracic Vertebrae

A typical thoracic vertebra is made up of a body and a neural arch (vertebral arch). Each vertebra has seven processes, i.e., four articular processes, two transverse processes, and one spinous process.

Body

The superior and inferior surfaces of the body of a typical vertebra are heart shaped

Bones Of The Thoracic Region A typical thoracic vertebra as seen from above

Bones Of The Thoracic Region A typical thoracic vertebra as seen from Lateral side

The lateral aspect of the body, close to its upper and lower borders, shows the presence of two costal demi-facets. The upper demi-facet is usually larger and is close to the pedicle.

It articulates with the numerically corresponding rib. The lower costal demi-facet is smaller and lies in front of the inferior vertebral notch and articulates with the lower rib.

Vertebral Arch

It consists of pedicles and laminae. Pedicles are short and directed backward. Laminae are short, thick, and flat vertical plates of the bone that join in the midline to form the posterior portion of the vertebral arch.

The superior vertebral notch is shallow and present above the pedicle while the inferior vertebral notch is deep and present below the pedicle. The vertebral foramen is small and circular. It is bounded by body, pedicles, and laminae.

Vertebral Arch Processes

The transverse processes are large, club-shaped, and directed laterally and somewhat backward. On their anterior surface, they bear, an oval costal facet for articulation with the tubercle of the rib (costotransverse articulation).

The costal facets on the upper six transverse processes are concave and directed anterolaterally. While the costal facets in the 7th to 10th transverse processes are flat and directed upwards, forwards, and laterally.

The superior articular facets are directed posterolaterally while the inferior articular facets are directed anteromedially. The spinous processes are long and directed downwards

A typical Thoracic Vertebra

First Thoracic Vertebra

  • The following features will help to identify the head of rib J’s first thoracic vertebra:
  • The body is like cervical vertebrae, i.e., its anteroposterior diameter is less than its transverse diameter.
  • There is the presence of a single circular costal facet on the lateral surface of the body for articulation with the head of the first rib.
  • Presence of a small costal demi-facet near its lower border for articulation with the upper demi-facet on the head of the 2nd rib.
  • The vertebral foramen is large and triangular (similar to the cervical vertebra).
  • The spinous process is long and directed backward

Bones Of The Thoracic Region First Thoracic Vertebra As Seen From Superior Aspect

Tenth Thoracic Vertebra

The shape of the body is somewhat like lumbar vertebrae.

Mostly it bears a single circular costal facet for the head of the 10th rib.

It means the head of the 10th rib will not articulate with the body of the 9th thoracic vertebra. Hence the body of the 9th vertebra will have only the upper demi-facet.

The costal facet is present on the anterior aspect of the transverse process for the tubercle of the 10th rib.

Bones Of The Thoracic Region The lateral Aspect Of 10th Thoracic Vertebra

Eleventh Thoracic Vertebra

  • The body is large and somewhat lumbar type.
  • A single circular costal facet on the lateral aspect of the body.
  • The transverse process is short and bears no costal facet, as the 11th rib is a floating rib.
  • The superior and inferior articular facets are thoracic type. (Sometimes inferior articular facet may be lumbar type).
  • The spinous process may be somewhat like a lumbar vertebra.

Twelfth Thoracic Vertebra

  • The body is large and lumbar-type (kidney-shaped).
  • The single circular costal facet for the head of the 12th rib. The facet is present mid-way between the upper and lower borders and tends to encroach on the lateral aspect of the pedicle.
  • Similar to the 11th vertebra there is the absence of costal facet on the transverse process.
  • The transverse processes of T12 are short (rudimentary) and present three tubercles, i.e., superior, inferior, and lateral. The lateral tubercle represents the true transverse process.
  • The inferior articular facets are lumbar-like, i.e., they are convex and face anterolaterally. The superior articular facets are thoracic type, i.e., flat and directed posterolaterally.
  • The spinous process is also like a lumbar vertebra, i.e., short, broad, and directed backward.
  • Articulation of a Typical Rib with the Vertebrae (Costovertebral and Costotransverse Joints)
  • A typical rib articulates posteriorly with the bodies of two adjacent vertebrae and the transverse process of the lower vertebra. Students should practice this articulation with the help of two typical thoracic vertebrae and a typical rib.

Bones Of The Thoracic Region Twelfth Thoracic Vertebra as seen From lateral side

The Costotransverse Joint

The articular part of the tubercle of the rib presents an oval facet. It articulates with the articular facet on the transverse process of the corresponding vertebra.

This can be further understood by looking at the articulation of the 7th rib. The head of the 7th rib articulates with the body of the 6th thoracic vertebra (with the demi-facet near its lower border) and with the body of 7th thoracic vertebra (with the demi-facet near its upper border).

The head is also connected with the intervertebral disc between the 6th and 7th thoracic vertebrae. The tubercle of the 7th rib also articulates with the transverse process of the 7th thoracic vertebra.

Bones Of The Thoracic Region Articulation Of A Typical Rib With Vertebrae

Ossification of Thoracic Vertebra

A typical thoracic vertebra ossifies by three primary centers, i.e., one for the body and one for each neural arch. These centers unite with each other between 3 to 5 years of age At puberty, five secondary centers appear, i.e., one for the spine, one for each transverse process, and two ring-like centers at the margin of the upper and lower surface of the body.

Tuberculosis of Thoracic Vertebrae Spongy bone in the body of thoracic vertebrae is the most common site of tubercular infection. Tubercular bacilli reach the spongy bone through blood circulation and settle there due to sluggish blood flow and restricted mobility of thoracic coloumn.

The infection leads to the destruction of spongy bone and the production of “Cold pus”. As the chronic injection of tubercle bacilli does not produce the local signs of heat, pain, and redness, it is called a cold abscess. Due to the destruction of spongy bone body is collapsed resulting in the production of kyphosis.

Bones Of The Thoracic Region Ossification By Primary Centers and Secondary Centers

Scoliosis and Kyphosis

The thoracic coloumn is the most common site where scoliosis and kyphosis are produced (See Further Details). Kyphosis is most commonly seen in old age due to weakness of spongy bones of vertebral bodies (Osteoporosis).

Bones Of The Thoracic Region Lateral Aspect Of A Part Of Thoracic Column

Hemivertebra

Sometimes the body of the vertebra ossifies by two primary centers, one for each lateral half of the body. If one of these centers fails to ossify then only half of the vertebral body is formed. This leads to the lateral bending of the column on one side.

Bones Of The Thoracic Region Schematic diagram showing the transmission of force from sternum to vertebral column through ribs

Bones Of The Vertebral Column Notes

Bones Of The Vertebral Column

The vertebral column is present in the central region of the body. It is the main constituent of the axial skeleton.

The column is also called as spine or backbone. The vertebral column extends from the base of the skull to the tip of the coccyx.

The vertebral column is composed of a series of many irregular bones called vertebrae. There are 33 vertebrae in the column, which are connected by intervertebral joints.

The important intervertebral joint is made up of a fibrocartilagenous intervertebral disc that binds the bodies of two adjacent vertebrae.

The length of the vertebral column is about 70 centimeters in an adult male. About l/4th length of the column is formed by intervertebral discs.

The adult vertebral column is divided into 5 different regions:

The Cervical Region: This part of the column is present in the neck and consists of seven cervical vertebrae.

The Thoracic Region: It is present in the thorax and consists of 12 thoracic vertebrae.

The Lumbar Region: It is present in the abdominal part and is made up of 5 lumbar vertebrae.

The Sacral Region: It is present in the pelvic region and consists of five fused sacral vertebrae. These five fused vertebrae are considered as a single bone, the sacrum.

The Coccygeal Region: It is present at the lower end of the column. It is usually a single bone, which is formed by the fusion of four coccygeal vertebrae.

Bones Of The Vertebral Column The vertebral column (spine) as seen from lateral side

When you shall view the articulated vertebral column from the front (anterior aspect) you shall notice the progressive increase in the width of the vertebral bodies from above downwards (from C2 to L5). This is because, at each vertebral segment, some more load is added to the column.

Read and Learn More Human Osteology Notes

Curves of the Vertebral Column

When viewed from the lateral side, the vertebral column of an adult shows four curvatures, i.e., cervical, thoracic, lumbar, and sacral.

  • The cervical and lumbar curves are convex anteriorly, while the thoracic and sacral curves are concave anteriorly.
  • The thoracic and sacral curvatures are called primary curvatures. They are present at the time of birth. These curvatures are formed mainly due to the shapes of vertebrae.
  • The cervical and lumbar curvatures are called secondary curvatures because they develop after birth. Cervical curvature develops after the child starts holding the head on the neck. The lumbar curvature develops after an infant assumes an upright posture and begins to walk. Thus secondary curvatures develop due to the posture.
  • In adults, cervical and lumbar intervertebral discs are thicker anteriorly thus contributing to anterior convexity. The posterior aspect of the column is formed by laminae, spinous processes, and articular facets.
  • The adjacent spinous process and laminae are inter¬ connected with the help of ligaments, while facets form joints.

Functions of the Vertebral Column

  • The vertebral column acts as a rigid but flexible column.
  • It transmits the weight of the body.
  • It supports the head.
  • The vertebral column protects the spinal cord and part of the spinal nerves.
  • It gives attachments to the ribs and muscles of the back.

Structure And Functions Of A Typical Vertebra

Bones Of The Vertebral Column The Curvatures Of Vertebral Column

In the following paragraphs, only the generalized description of vertebrae is given.

Vertebral Body The detailed description of cervical vertebrae is given in Chapter 7, thoracic vertebrae in Chapter 5, and lumbar, sacral, and coccyx in Chapter 6.

Though the vertebrae of different regions of the vertebral column vary in size, shape, and other characteristics many basic features are common in these vertebrae.

A vertebra from the mid-thoracic region is best suited to study the basic features of a typical vertebra.

The following description of a typical vertebra is based on the features of a mid-thoracic vertebra.

A typical vertebra consists of:

  • A vertebral body.
  • A vertebral (neural) arch with seven processes.

Bones Of The Vertebral Column A typical thoracic vertebra as seen from superior aspect

Bones Of The Vertebral Column A typical thoracic vertebra as seen from lateral aspect

Vertebral Body

  • Hold a typical thoracic vertebra in your hand and note the following:
  • The body of a vertebra is situated anteriorly. It is somewhat cylindrical.
  • The cylindrical body is rounded from side to side. Its superior and inferior surfaces are flat.
  • Thus the body has six surfaces (anterior, posterior, superior, inferior, and two lateral).
  • The anterior, lateral, and posterior surfaces contain minute foramina for the vessels.
  • The body is made up of spongy bone and covered by a thin layer of compact bone.
  • However, its superior and inferior surfaces are not covered by compact bone but by a thin layer of hyaline cartilage in living persons. The upper and lower surfaces give attachments to the intervertebral discs.

Vertebral Arch

The vertebral arch is situated posterior to the body of the vertebra. It consists of a pair of pedicles and laminae. Seven processes arise from the vertebral arch of a typical vertebra.

Pedicles.

  • The pedicles are short, stout bars that are attached to the posterolateral aspects of the body.
  • They are attached close to the superior border of the body.
  • Pedicles project posteriorly and somewhat laterally from the body to unite with the laminae.
  • If we look at the lateral aspect of a vertebra there is the presence of an inferior vertebral notch just below the pedicle.
  • This notch is bounded anteriorly by the body superiorly by the pedicle and posteriorly by the inferior articular process.
  • The superior vertebral notch is situated above The pedicle. It is much shallower as compared to the inferior vertebral notch.

Laminae

  • These are flat vertical plates of the bone that join in the midline to form the posterior portion of the vertebral arch.
  • They extend backward and medially from the pedicles.
  • Posteriorly, the lamina of the right and left sides fuse in the midline to form a spinous process.
  • The body, pedicles, and laminae of a vertebra together enclose a foramen called vertebral foramen.
  • Collectively the vertebral foramina of the successive vertebrae form the vertebral canal that transmits the spinal cord.

Transverse Processes

The transverse process extends laterally on each side from the point where the lamina and pedicle join each other.

Articular Processes

There are two superior and two inferior articular processes. They also arise from the junction of pedicle and lamina.

Each particular process bears a smooth articular facet. In the thoracic vertebrae, the superior articular facets face posterolaterally, while the inferior ones face anteromedially.

Spinous Process

It projects posteroinferiorly in the midline from the junction of two laminae

Functions of the Various Components of a Vertebra

  • The bodies and intervertebral discs are involved in the transmission of the load of the trunk to the lower limbs.
  • The intervertebral discs are shock absorbers and also permit various movements between two successive bodies.
  • Articular processes (and facet joints) allow and guide the movements between adjacent vertebrae.
  • Facet joints are also involved in the transmission of load. The magnitude of the load transmitted by facet joints varies in various regions of the column, i.e., cervical and lumbar facets are highly loaded while thoracic is least loaded.
  • Lamina is also involved in the transmission of load as it passes from superior to inferior articular facet joints.
  • In the thoracic region, where the column is concave anteriorly, the load passes from the vertebral arch (lamina) to the body.
  • While, in the lumbar region, where the column is concave posteriorly, load passes from the body to the vertebral arch. The transmission of load between the body and the vertebral arch is through the pedicles.
  • The spinal cord and its meninges are well protected in the vertebral foramen (canal).
  • The transverse and spinous processes give attachment to muscles and act as levers for various movements of the vertebral column.
  • Transverse processes in the thoracic region are also involved in the transmission of load from the ribs to the laminae.

Articulation between Two Successive Typical Vertebrae

The articulations between two successive thoracic vertebrae are. Adjacent vertebrae are connected at three intervertebral joints, i.e., one median joint between bodies and two joints between the articular processes of successive vertebrae.

The two adjacent vertebral bodies are joined by the intervertebral disc, which is made up of fibrocartilage. Each disc consists of annulus fibrosus (outer fibrous part) and nucleus pulposus (inner soft part).

The two superior articular processes of a vertebra articulate with the two inferior articular processes of the vertebra situated above it.

Similarly, two inferior articular processes of the vertebra articulate with the two superior articular processes of the vertebra situated below it.

The joints between articular processes are synovial and are also known as facet joints.

The vertebral foramina of the successive vertebrae forms a continuous vertebral canal, that contains the spinal cord and its meninges. The superior and inferior vertebral notches of the adjacent vertebrae join to form the intervertebral foramen through which passes the spinal nerves and vessels.

Bones Of The Vertebral Column Joints between two successive thoracic vertebrae

Bones Of The Vertebral Column The diagrammatic representation to show the structure of intervertebral disc

The boundaries of intervertebral foramen are formed anteriorly by the body of the upper vertebra, the intervertebral disc, and a small part of the body of the lower vertebra.

The upper and lower boundaries are formed by pedicles of the upper and lower vertebrae respectively. The posterior boundary is formed by the lamina of the upper vertebra and facet joint

The articular facets are present on the body and transverse processes of the thoracic vertebra. These are called costal facets.

The costal facets of adjacent bodies articulate with the head of the rib. The facet on the transverse process articulates with the tubercle of the rib.

Principle Distinguishing Features of the Vertebrae of the Various Regions of the Vertebral Column Besides the features mentioned, the following features will help students to distinguish cervical, thoracic, and lumbar vertebrae from one another:

A cervical vertebra can be easily identified because of the presence of a foramen in its transverse process. This foramen is called as foramen transversarium.

A thoracic vertebra is recognized by the presence of articular facets on the body and transverse processes. These facets are called costal facets, which articulate with the ribs.

A lumbar vertebra is recognized because it has a large kidney-shaped body. There is the absence of foramen transversarum in the transverse processes. There is also the absence of costal facets on the body and transverse processes.

The sacrum is easily identified because of its shape. As it is formed by the fusion of five sacral vertebrae, it is a single, curved, and triangular bone.

The coccyx is formed by the fusion of four coccygeal vertebrae. Coccyx is identified by its small size and fused nature.

Bones Of The Vertebral Column As seen in lateral aspect of column

Bones Of The Vertebral Column As seen in the transverse section of column

 

Bones Of The Vertebral Column Comparsion Of Structural Features Of Typical Cervical throracic and lumbar vertebrae

Bones Of The Vertebral Column A typical cervical vertebra as seen from superior aspect

Bones Of The Vertebral Column Typical lumbar vertebra as seen from superior aspect

Bones Of The Vertebral Column Sacrum and coccyx as seen from anterior aspect

Movements Occurring in the Vertebral Column

As the sacral and coccygeal vertebrae are fused, no movements are possible between these vertebrae.

The cervical, thoracic, and lumbar vertebrae are not fused hence, are mobile.

Two adjacent vertebrae are joined with each other at three intervertebral joints, i.e., by intervertebral disc (between two adjacent bodies) and by two synovial joints (between articular. processes).

The movements between two adjacent vertebrae are slight. But when movements between series of vertebrae are added, the column shows considerable flexibility.

Bones Of The Vertebral Column Superior Aspect Of Typical Cervical

Bones Of The Vertebral Column Superior Aspect Of Typical Cervical.2

Bones Of The Vertebral Column Superior View Of Sacrum

Bones Of The Vertebral Column Right Lateral And Posterior View Of Articulated Thoracic Column

The following movements are possible in the vertebral column:

  • Flexion: Forward bending.
  • Extension: Backward bending.
  • Lateral flexion: Side bending.
  • Rotation: Twisting.

In different regions, i.e., cervical and lumbar regions are more mobile as compared to thoracic. Almost all types of movements are possible in the cervical region.

Rotation movement is the main movement of the thoracic region, but this movement is not possible in the lumbar region.

Particular Features of a Typical Vertebra

There are many ligaments, which connect adjoining vertebrae. With the help of these ligaments and intervertebral joints, a flexible but rigid column is formed.

Attachments of Ligaments

The anterior longitudinal ligament is attached to the anterior surfaces of the bodies of successive vertebrae. It is a continuous ligament, which extends from the base of the skull to the sacrum.

The posterior longitudinal ligament is also continuous and attached to the posterior surface of the bodies of vertebrae.

The transverse processes of the adjacent vertebrae are connected by intertransverse ligaments.

Bones Of The Vertebral Column Attachment Of Various Ligaments On A Vertebra

Bones Of The Vertebral Column Movements Of the Vertabal Column

  • The Ligamentum flava connects the laminae of adjacent vertebrae.
  • Similarly, the spinous processes of adjacent vertebrae are connected by interspinous ligaments.
  • In the cervical region, the tips of the spines are connected by the elastic ligament, called as ligamentum nuchae.
  • The supraspinous ligaments are attached to the tips of spinous processes of vertebrae between the 7th cervical vertebra to the sacrum.

Attachments of Muscles

  • Various muscles are attached to the various aspects of vertebrae in different vertebral regions. The attachments of these muscles are described along with the bones of that region.

Clinical importance

Abnormal Curvatures

Following abnormal curvature may be present in the vertebral column:

Kyphosis

This is due to the abnormal increase in the thoracic curvature (increase in the thoracic concavity anteriorly). It is usually seen in old age due to osteoporosis. The osteoporosis leads to the erosion of the anterior part of one or more vertebrae, leading to an increase in concavity.

Lordosis

This is due to the abnormal increase in lumbar curvature (increase in the lumbar convexity anteriorly). This results due to the weakness of the abdominal muscles.

Lordosis may also occur in obese people and pregnant ladies. This is due to the shift in the line of gravity because of an increase in the weight of abdominal contents.

Scoliosis

It is the most common deformity of the vertebral column and is predominantly observed in girls in the teens. In this condition, there is an abnormal lateral curvature associated with the rotation of the vertebrae.

In most cases, the cause of the scoliosis is not known. Known causes are hemivertebra, maldevelopment of one upper limb, and asymmetry in the length of the lower limbs.

Fractures

The fracture of the vertebral column may occur due to forceful flexion or hyperextension of the column.

The forceful sudden flexion of the column may occur due to a fall from the height of the feet or the head. This leads to the impression of fracture and dislocation of one or more successive vertebrae.

This kind of fracture may be associated with the injury to the spinal cord resulting in loss of sensation and paralysis of muscles below the level of injury.

Bones Of The Vertebral Column Kyphosis Is An Increases In Thronic Concavity

Bones Of The Vertebral Column Lordosis Is An Increase In Lumbar Convexity

Bones Of The Vertebral Column Scoliosis Is Abnormal Lateral Curve

Spondylolysis

In this condition there occurs the breakage (cleft) in the vertebral arch (at lamina between superior and inferior articular processes) of one or both sides. This condition is common in the lower lumbar region. Spondylolysis may result due to excessive mechanical stress.

It is now considered as the fatigue fracture of the lamina. This condition is different from spondylolisthesis (described below). In spondylolysis, there is no displace¬ ment of the vertebral body and it is often asymptomatic (without pain).

Tuberculosis of the Spine

The vertebral bodies are the common sites for the tubercular infection. This is due to the spongy nature of the vertebral body and rich blood supply. Due to the infection, the spongy bone of the body is destroyed and pus is formed. This leads to the collapse of vertebral bodies as the load of the trunk is brought by the upper vertebrae.

Human Osteology Introduction

Human Osteology Introduction

The subject of “Human Anatomy” is mainly studied with the help of the dissection of cadavers (dead bodies).

The structure of various parts of the body (i.e., muscles, blood vessels, nerves, joints, and organs) and their interrelationship can be easily seen by the dissection of dead bodies.

All these soft structures are arranged around bones, i.e., muscles and ligaments are attached to bones while, nerves, vessels, and other soft structures are related (or present) close to the bones.

It should also be realized that bones form the skeletal framework of the body and, therefore, give shape to the body.

Hence, for a proper understanding of the gross anatomy of any region, it is essential to learn the structure of bones of that region first, i.e., before starting the dissection of that region.

Students should note that gross anatomy can’t be learned without a sound knowledge of osteology.

What is Osteology?
Osteology is a branch of gross anatomy, which deals with the study of bones.

Parts Of The Skeletal System

The skeletal system consists of bones and cartilage. The cartilage is present at the ends of the bone. The skeletal system consists of two main parts, i.e., axial and appendicular skeleton.

The Axial Skeleton consists of bones lying close to the central axis of the body, e.g., skull, vertebrae, sacrum, coccyx, hyoid bone, sternum, and ribs.

The Appendicular Skeleton It consists of the bones of the upper limb and lower limb including bones forming shoulder and pelvic girdles.

Read and Learn More Human Osteology Notes

How many bones are present in a human skeleton? There are approximately 206 bones present in an adult human. Out of these 80 are present in the axial skeleton and 126 in the appendicular skeleton.

Human Osteology Introduction Number Of Bones Present In Axial And Appendicular Skeleton

The total number of bones in the human body may exceed 206. This is because some accessory (supernumerary) bones may appear especially in the skull and lower limbs.

Bone Structure

Bone is a dynamic living tissue of the body. It is a constantly changing tissue, i.e., old bone tissues are constantly replaced by new ones.

Bone is composed of cells and intercellular matrix. Bundles of collagen fibers are embedded in the matrix. It is hard because of the deposition of calcium salts in the matrix.

Gross (Macroscopic) Structure of An Adult Living Long Bone.

A typical long bone (bone of limb) consists of a shaft or body and two ends. Both the ends of a bone are knobby (enlarged) and are covered by articular cartilage. The shaft of a long bone lies between two ends.

It is narrow in the middle and expanded towards each end. It encloses a cavity called a marrow cavity, which in an adult is filled with yellow bone marrow.

The entire bone is covered with a fibrous membrane (periosteum) except for the areas covered by articular cartilage.

Human Osteology Introduction The Parts Of A Long Bone

Blood vessels and nerves enter the bone through numerous foramina present near the ends and at the middle of the shaft. The prominent foramen of the shaft is called as nutrient foramen.

Further details of a living long bone may be studied by observing a longitudinal section of any long bone from the upper or lower limb.

The section reveals two different kinds 0f bones, i.e., compact and spongy.

Compact Bone

The compact bone is a dense bone in which no spaces are visible on naked eye examination. Its texture is like an ivory.

Though the compact bone covers the entire bone it is well developed in the shaft or body. The compact bone of the shaft encloses the marrow cavity filled with bone marrow.

Human Osteology Introduction Longitudinal Section Of A Long Bone To Show Compact And Spongy Bones And Various Other Parts

Spongy or Trabecular Bone

It is also known as cancellous bone. Spongy bone is a meshwork of bony spicules (small rods and thin curved plates), which enclose large spaces.

The spongy bone occurs at the ends of a long bone. On the outer surface, the spongy bone is always covered with a thin layer of compact bone. The spaces between spicules are filled with red bone marrow

Parts of a Living Long Bone

From the above description it becomes evident that a living long bone consists of the following parts:

  1. Shaft or body (Diaphysis and Metaphyses).
  2. Two ends (Epiphyses).
  3. Articular cartilage.
  4. Periosteum.
  5. Endosteum.
  6. Medullary cavity.
  7. Bone marrow.

1. Shaft or Body

The shaft of a long bone is a long, cylindrical (tubular) structure, made up of compact bone. It is also called diaphysis.

It encloses a tubular space called a marrow cavity. The compact bone of the shaft provides support and bears the weight. It is also capable of resisting the various stresses produced by movements.

The expanded distal ends of the shaft or body, where they meet with the articular ends (epiphyses), are called metaphyses.

2. Two Ends of Proximal and Distal

Two ends (proximal and distal) are expanded and made up of spongy bone covered with a thin layer of compact bone. At the ends, a long bone forms synovial joints and thus comes in contact with other bones. The ends are covered by hyaline cartilage. This particular end of a long bone is also called an epiphysis.

3. Articular Cartilage

As stated earlier the ends of a long bone are covered by a thin layer of hyaline cartilage at the site where bone comes in contact with other bone (forms a joint). The articular cartilage provides a smooth surface thus reducing friction between two bones during movements. It also helps in the absorption of shock during movements.

4. Periosteum

The entire outer surface of the bone (except where it is covered by articular cartilage) is covered with a tough sheath of dense connective tissue. This membrane is attached to the bone tissue by Sharpey’s fibers.

The periosteum consists of an outer layer of collagen fibers and fibroblasts and an inner layer of fibroblasts-like cells called osteoprogenitor cells.

The osteoprogenitor cells have the potential to divide and change to osteoblasts (bone-forming cells).

The periosteum serves the following functions:

  1. It forms an outer limit of bone and thus maintains its shape. It also protects the bone.
  2. The periosteum contains bone-forming cells, which help the bone to grow in diameter.
  3. It is richly supplied with blood vessels thus helping in providing nutrition to bone and assisting in fracture repair.
  4. It is also richly supplied with sensory nerves, making it sensitive to pain.
  5. Periosteum provides attachment to ligaments, tendons, muscles, intermuscular septa, and articular capsule of a joint

5. Endosteum

The endosteum is a cellular membrane that lines the medullary cavity of the shaft and the medullary spaces of spongy bone at the ends. It is composed of a single layer of flattened osteoprogenitor cells and a very small amount of connective tissue.

6. Medullary or Marrow Cavity

It is a space within the shaft or body of a long bone. The marrow cavity of the shaft is continuous with the spaces of spongy bone at the ends.

7. Bone Marrow

The marrow cavity of a newborn is filled with red bone marrow that is actively involved in the formation of blood. Red bone marrow consists of adipose and hemopoietic (blood-forming) tissues.

However, with the advancing age, the red marrow in the shaft of bone is replaced by yellow marrow (fatty marrow), which is unable to produce blood cells.

In adults, red marrow only remains at the ends of long bones, sternum ribs, skull bones, and vertebrae. At these places, red marrow is actively involved in the production of blood cells throughout life.

Some important facts about the bone

Students should note that the above description is of a living bone (bone present in a living person).

They should realize that the bones, that they handle in the classroom, are dry and I devoid of many structural components of a living bone.

For example, a dry bone is not covered by hyaline cartilage at its epiphyseal ends. Similarly, it is also devoid of periosteum, endosteum, bone marrow, blood vessels, and nerves.

Bone is not only a living tissue but it is also a dynamic tissue. It is continuously engaged in building new bone and breaking down the old bone.

Students should also realize that each living bone is not just a bone tissue but somewhat similar to an organ.

It is evident by the fact that a bone consists of not only bone tissue proper but also many other tissues like fibrous membranes (periosteum and endosteum), cartilage (articular cartilage), bone marrow (adipose and hemopoietic tissues), nerves and blood vessels.

Similar to any other organ of the body, bone is also involved in various functional activities (locomotion, support, and protection of delicate organs, formation of blood, and storage of calcium).

Features on the surface of dry bone (bone markings)

In your osteology classroom, you will handle the dead dried bones to learn their general features. The structures, which are attached to a bone or are in close contact with it, in living conditions, leave marks on the bone surface.

The following kinds of bony features (smooth areas, surface elevations, surface depressions, and foramina) can be observed on the surface of dried bones:

Smooth Areas

The smooth areas on a bone are found at places where it gives attachment to muscle fibers; where it is covered by articular cartilage; and where it lies directly beneath the skin in living conditions.

Facet

It is a flat and smooth area on the bone. In a living state, it is covered with articular cartilage, e.g., articular facets on the surface of carpal and tarsal bones.

Human Osteology Introduction Articular Facts On The Calcaneus

Surface Elevations

These are of many types, i.e., crest, line, lip, and ridge are elongated surface elevations. While tubercle, tuberosity, epicondyle, and trochanter are irregular elevations.

These surface elevations are mostly due to the attachment of tendons, ligaments, or aponeurosis. Some surface elevations are sharp like the spine, cornu, or styloid process.

Crest: It is a bony ridge, which may be quite wide, e.g., the iliac crest of the hip bone or narrow, e.g., the external occipital crest.

Human Osteology Introduction The iliac crest of hip bone

Line: An elevated line on the surface of the bone, e.g., the sole line of the tibia and superior nuchal line of occipital bone.

Human Osteology Introduction The soleal line of tibia

Condyle: A bony mass, that may have a somewhat rounded or circular articular area, e.g., condyles of the femur.

Human Osteology Introduction Condyles, epicondyles and tubercle at the lower end of femur

Epicondyle: Bony eminence (protuberance) situated on the surface of the condyle, e.g., lateral and medial epicondyle of the femur.

Human Osteology Introduction The occipital bone showing crest, nuchal lines and protuberance

Protuberance: A projection from the surface of the bone, e.g., the external occipital protuberance.

Malleolus: It is a rounded bony process, e.g., the medial malleolus of fiber

Spinous process: A spine-like projection, e.g., the spinous process of a vertebra

Trochanter: It is a large blunt elevation from the surface of the bone, e.g., greater and lesser trochanters of the femur.

Human Osteology Introduction Large, rounded elevation of tibia malleolus

Human Osteology Introduction The spinous process of vertebra

Human Osteology Introduction The greater and lesser trochanters of femur

Tuberosity: A large rounded elevation, e.g., the ischial tuberosity

Human Osteology Introduction Tuberosity is a large elevation while notch is a deep indentation

Tubercle: A raised elevation, but smaller than trochanter, e.g., adductor tubercle of femur

Human Osteology Introduction The bicipital Groove Of Humerus is the elongated deperession

Surface Depressions and Foramina

Groove or is an elongated depression on the sulcus: the surface of the bone, e.g., the bicipital groove of the humerus.

The groove or sulcus on a dry bone indicates that the bone in living condition was concerning blood vessels or tendon relation to blood Iliac crest iliac fossa vessels or tendon

Notch: It is a deep indentation at the border of a bone, e.g., greater and lesser sciatic notches of the hip bone and suprascapular notch of the scapula.

Human Osteology Introduction Notch At the Upeer Border Of Scapula

Fossa: A depression on the surface of the bone, e.g., the iliac fossa of the hip bone and the olecranon fossa of the humerus.

Foramina: Bones show many openings on the surface, i.e., canals and foramina. A canal is a tunnel-like passage with one opening at each end. These are usually for the passage of blood vessels and nerves.

A bone may also show some other surface features, which you must learn with the help of your teachers.

Human Osteology Introduction The Olecranon Fosaa At the lower End of humerus

How to study a bone?

Following guidelines will be of help when you are learning any particular bone for the first time.

While you are studying a bone you should have the same bone before you. There is no sense in reading about a bone, from a book, without having that bone in your hand.

The first step in learning a bone is to identify its ends (upper end, lower end, etc.), borders, and surfaces. This can be learned with the help of your teachers or with the help of diagrams from this book.

The second step is to identify some of the important projections (e.g., spine, tubercle, ridge, condyle, etc.) and depressions (e.g., fossa, foramen, notch, etc.), if present on the bone.

Side Determination of the Bone

Once you have identified the ends, borders, and surfaces and some of the bony features you will be able to determine the side of the bone.

Take the help of your teachers to know which are the bony features of that particular bone which will help to determine the side of bone.

(In the case of bones belonging to the axial skeleton there is no need to determine the side as many of them are unpaired, i.e., some bones of the skull, vertebrae, etc.). Side determination of the Lateral bone is very important.

Bone Anatomical Position

The next step is to learn to hold the bone in an anatomical position. Once you have determined the side of the bone hold it in the position it occupies in the body (as in anatomical position).

All the description of the bone in the textbooks is given considering the position of the bone in an upright posture (anatomical position).

If the bone, while studying, is not held in an anatomical position, confusion will arise regarding its borders and surfaces.

Bone General Features

Now learn the bony features (“General Features”) of bone in detail. After understanding the general feature it will become very easy to know the side of the bone and to keep it in the anatomical position.

Bone Particular Features

Once you have understood the general features of a bone it is now time to study the “particular features” (attachments of muscles and ligaments and relations of nerves and vessels).

This can be practiced by marking the area of origin of the muscle with red chalk and insertion of muscle with blue chalk on the surface of the bone. All the sites for attachments of ligaments should be marked with green chalk.

Mark the area of bone, which is with the nerve, by a solid line with yellow chalk. Similarly, the relation of artery and vein on the surface of a bone can be marked with the red and blue lines respectively.

Bone Anatomical Position Ossification

You may also study the ossification of bone if needed. (Ask your teacher whether you are supposed to know the ossification or not?).

Note the age of appearance of primary centers, secondary centers, and the time of fusion of primary with secondary centers.

Also, note which ends of a long bone is a “growing end”. Students are suggested to learn about the “ossification” and “growing end of bone” from a book of “General Anatomy.

Bone Anatomical Position Clinical Importance

Lastly, you should also learn the “applied” or “clinical importance” of the bone, if any.

Bones Of The Lower Limb Notes

Bones Of The Lower Limb

The lower limb consists of many regions. The following bones are present in various regions of the lower limb:

Pelvic (Hip) Region

Bones of Pelvic (Hip) Region region form the pelvic girdle. The pelvic girdle consists of two hip bones. These bones are united to each other in the midline anteriorly to form a joint known as the pubic symphysis.

Both the hip bones unite posteriorly with the sacrum at the sacroiliac joint. The pelvic girdle (two hip bones) and sacrum together form a basin-like structure called a bony pelvis.

Thigh Bones

This region consists of a single bone called as femur. The upper end of this bone articulates with a hip bone to form a hip joint. The lower end of the femur articulates with the upper end of the tibia to form the knee joint.

Leg Bones

This region consists of two long bones, i.e., medially placed tibia and laterally placed fibula. These two bones, at their lower end, articulate with talus to form ankle joint.

Foot Bones

The skeleton of the foot consists of many bones, i.e., tarsals, metatarsals, and phalanges. These bones form many joints, i.e., intertarsal, tarsometatarsal, metatarsophalangeal, and interphalangeal.

Bones Of The Lower Limb Schematic Diagram Showing Bones Of Lower Limb

Hip Bone

The hip bone is n large, irregular, and flat bone. The middle portion of the bone is constricted and carries a cup-shaped deep cavity on the lateral aspect of the bone. This cavity is known as the acetabulum. The bone is expanded above and below the acetabulum.

Read and Learn More Human Osteology Notes

There is the presence of a large oval or triangular aperture just below and medial to the acetabulum. It is called as obturator foramen.

The bone above the acetabulum is expanded and flat. This portion is called ilium. The bone below the acetabulum consists of two parts, i.e., the anterior and inferior, pubis and posterior and inferior, ischium.

(Though an adult hip bone is a single bone at birth each hip bone consists of three separate primary bones, i.e., ilium, ischium, and pubis.

These three bones are joined to each other by a Y-shaped tri-radiate hyaline cartilage. These three components of hip bones join each other at the acetabulum. However, these three bones begin to fuse at 15 to 17 years of age.

Bones Of The Lower Limb Lateral view of the right hip bone

Bones Of The Lower Limb In a young hip bone tri-radiate cartilage separtes three parts of right hip bone

Though in an adult bone, the site of fusion is not visible between three bones, their names are still used as three parts of hip bone). In Fig. 3.4 medial view of the hip bone is shown.

Hip Bone Side Determination

Take the help of your teacher to determine the side of the hip bone

Bones Of The Lower Limb Medial view of right hip bone

  • The expanded flat part called as ilium, should be kept upwards (superiorly).
  • The other expanded part (pubis and ischium) with the obturator foramen should be kept downwards (interiorly).
  • The acetabulum should face laterally.
  • The lower expanded part (below the acetabulum) has two parts, i.e., thin pubis and thick ischium. The pubis should be directed anteriorly and the ischium posteriorly.
  • Many students find it difficult to keep the bone in an anatomical position.
  • Therefore you should learn the anatomical position of this bone only after you have learned the general features of all three parts (ilium, ischium, and pubis).

Ilium

Ilium is the largest part of the hip bone. It forms the upper fan-shaped expanded part above the acetabulum. The upper 2/5th of the acetabulum is formed by the ilium.

Ilium General Features

The ilium presents:

  • Two ends-Upper and lower.
  • Three borders-Anterior, posterior, and medial.
  • Three surfaces-Gluteal (lateral), iliac fossa, and sacropelvic.

ilium Ends

  • Upper end-The upper end is in the form of an expanded border. It is also called an iliac crest. The iliac crest is a thick and curved border, which is convex upwards.
  • This extends between two projections, i.e., anterior superior iliac spine and posterior superior iliac spine.
  • The iliac crest is subdivided into ventral and dorsal segments.
  • The ventral segment is anterior 2/3rd of the iliac crest and presents an outward convexity, while the dorsal segment forms posterior 1/3 of the crest and presents outward concavity.
  • The thick ventral segment of the iliac crest shows an outer lip, intermediate area, and inner lip.
  • The outer lip presents a prominence about 5 cm behind the anterior superior iliac spine. This is called as tubercle of the iliac crest.
  • The dorsal segment of the iliac crest presents medial and lateral sloping surfaces separated by a ridge.

Lower end-The lower end of the ilium lies in the acetabulum and forms the upper 2/5th of this cup-shaped cavity. At the lower end, ilium becomes continuous with the ischium and pubis. The lower end of the ilium meets with the pubis at iliopubic eminence.

Ilium Borders

Anterior border The anterior border of the ilium extends from the anterior superior iliac spine to the acetabulum. The lowest part of this border projects forwards, near the upper margin of the acetabulum, to form the anterior inferior iliac spine.

The posterior border extends from the posterior superior iliac spine to the greater sciatic notch.

Here it becomes continuous with the upper end of the posterior border of the ischium. This border presents a posterior inferior iliac spine and greater sciatic notch.

Medial border The medial border is present on the inner aspect (medial surface) of the ilium. This border extends from the iliac crest to the iliopubic eminence.

It lies between the iliac fossa and the sapropelic surface of the ileum. The medial border is rough in its upper l/3rd, sharp in its middle third, and rounded in the lower l/3rd. The lower one-third of the medial border is called an arcuate line.

Ilium Surfaces

The ilium has an outer gluteal surface and an inner surface, which is further divided into the iliac fossa and sapropelic surface.

The gluteal surface surface is the lateral surface (outer aspect) of the ilium. It has three rough curved lines (the posterior, anterior, and inferior gluteal lines), which divide the gluteal surface into four areas.

Iliac fossa-The iliac fossa is present on the anterior part of the medial surface of the ilium, in front of the medial border. The Iliac fossa presents shallow concavity and has a smooth surface.

The sapropelic surface is also present on the medial surface of the ilium behind the iliac fossa and medial border. It is subdivided into three parts, i.e., iliac tuberosity, auricular surface, and pelvic surface.

The iliac tuberosity is the upper rough part.

The auricular surface is ear-shaped and articular. It is the middle part of the sacropelvic surface, which articulates with the sacrum to form the sacroiliac joint.

The pelvic surface is the smooth surface below and in front of the auricular surface. This surface is continuous with the pelvic surface of the ischium. This surface may present a pre-auricular sulcus in the females who have given birth to children (multiparous).

Pubis

The pubis or pubic bone is situated ventromedial to ilium and ischium. It consists of a body, a superior ramus, and an inferior ramus.

Body of Pubis

The body is flattened and presents three surfaces, i.e., anterior, posterior (pelvic), and medial (symphyseal). The anterior surface faces downwards, forward, and laterally. The posterior surface is smooth and directed upwards and backward.

The symphyseal surface articulates with the corresponding surface of the opposite pubic bone to form a joint known as a pubic symphysis. This surface shows the presence of ridges that change with increasing age (See Further Details).

The superior border of the body of the pubis is thick and known as a pubic crest. At the lateral end of the pubic crest, there is a projection, the pubic tubercle.

Superior Ramus of Pubis

The superior ramus of the pubis arises from the upper and lateral parts of the body of the pubis.

Laterally it extends above the obturator foramen upto the iliopubic eminence where it joins the ilium. Here it also forms the pubic part (anterior 1/5) of the acetabulum. It has three borders (anterior, posterior, and inferior) and three surfaces (pectineal, pelvic, and obturator).

Pubis Borders

  • The anterior border is also known as the obturator crest and extends from the pubic tubercle to the acetabular notch.
  • The posterior border or pectineal line (pecten pubis) extends from the pubic tubercle to the iliopubic eminence.
  • It is a sharp border, which behind the iliopubic eminence becomes continuous with the arcuate line of ilium.
  • The inferior border forms the upper border of the obturator foramen.

Pubis Surfaces

  • The pectineal surface is situated between the pectineal line and the obturator crest. It is triangular and extends between the pubic tubercle and iliopubic eminence.
  • The pelvic surface lies between the pectineal and inferior border of the superior ramus. It is smooth and continuous medially with the pelvic surface of the body of the pubis.
  • The obturator surface is situated between the obturator crest and the inferior border. It is a grooved surface and forms the upper boundary of the obturator canal.

Inferior Ramus of Pubis

It extends downwards and laterally from the lower and lateral parts of the body of the pubis. The inferior ramus of the pubis meets the ramus of the ischium to form the conjoined ischiopubic rami. The conjoined ischiopubic rami form the medial boundary of the obturator foramen. It has an anterior and a posterior surface.

Ischium

The ischium forms the posteroinferior part of the hip bone. It consists of a body and a ramus.

Ischium Body

The body lies postero inferior to the acetabulum. It has two ends (upper and lower), three borders (anterior, posterior, and lateral), and three surfaces (femoral, dorsal, and pelvic).

Ischium Ends

  • The upper end of the body forms the 2/5 of the posterior and the inferior part of the acetabulum.
  • The lower end forms the ischial tuberosity. The ramus of the ischium extends from the lower end of the body upwards, forwards, and medially to meet the inferior ramus of the pubis.

Ischium Borders

  • The anterior border forms the posterior margin of the obturator foramen.
  • The posterior border is continuous with the posterior border of the ilium. It presents a triangular projection called an ischial spine.
  • The ischial spine is placed between the greater sciatic notch (above) and the lesser sciatic notch (below).
  • The lateral border extends from the lower margin of the acetabulum and becomes continuous with the lateral margin of the ischial tuberosity.

Ischium Surfaces

  • The femoral surface is situated between the anterior and lateral borders.
  • The dorsal surface is continuous above the gluteal surface of the ilium. The lower part of the dorsal surface has a large rough area known as ischial tuberosity.

Bones Of The Lower Limb Schematic diagram showing the ischial tubersosity

  • This tuberosity is divided by a transverse ridge in an upper quadrilateral part and a lower triangular part. Each of these parts (upper and lower) is again divided into medial land lateral parts.
  • The pelvic surface of the ischium is smooth and lies between the anterior and posterior borders.

Ramus of Ischium

  • It extends from the lower part of the body and runs upwards, forwards, and medially.
  • Here it meets the inferior ramus of the pubis and forms the conjoined ischiopubic ramus.
  • The conjoined ischiopubic ramus presents upper and lower borders and an outer and inner surface.

Obturator Foramen

It is a large triangular or oval foramen in the lower part of the hip bone. It is situated between the pubis and ischium.

The obturator foramen is bounded above by the superior ramus of the pubis, medially by the body of the pubis and conjoined ischiopubic ramus, and laterally by the body of the ischium.

Acetabulum

  • The acetabulum is a deep cup-shaped cavity facing laterally and anterior inferiorly. It is situated on the constricted middle part of the hip bone. All three parts of the hip bone (pubis, ischium, and ilium) contribute to its formation.
  • The acetabulum articulates with the head of the femur to form the hip joint.
  • The margin of the acetabulum is sharp and deficient in the anteroinferior part. This gap in the margin is called an acetabular notch.
  • The floor of the acetabulum has a horseshoe-shaped articular surface (lunate surface) and a non-articular central acetabular fossa.

Anatomical Position of Hip Bone Keeps the bone in such a way that:

  • The pubic bone lies anteriorly and the symphyseal surface of the pubis lies in the median plane.
  • The acetabulum faces laterally and slightly anteriorly.
  • The pubic tubercle and anterior superior iliac spine should lie in the same coronal plane.
  • The posterior surface of the body of the pubic bone should face postero-superiorly.
  • The ischial spine and superior end of the pubic symphysis are approximately in the same horizontal plane.

Acetabulum Particular Features

Ilium

Bones Of The Lower Limb Attachments on the left iliac crest

  • The external oblique muscle of the abdomen is inserted on the outer lip into the anterior 2/3rd of a ventral segment of the iliac crest.
  • The internal oblique originates from the intermediate area of the ventral segment of the iliac crest.
  • The inner lip gives origin to transverse abdominis.
  • The tensor-fascia lata muscle arises from the outer lip of the iliac crest near its anterior part.
  • Part of the latissimus dorsi arises from the posterior most of the outer lip of the ventral segment.
  • The quadratus lumborum arises from the posterior one-third of the inner lip of the ventral segment of the iliac crest.

Attachment of the Muscles on the Dorsal 1/3rd of the Iliac Crest

  • The lateral surface of the dorsal segment of the iliac crest gives origin to the gluteus maximus muscle.
  • The erector spinae arises from the medial surface of the dorsal segment of the iliac crest.
  • Attachment of the Muscles on the Outer Surface (Gluteal Surface) of Ilium.
  • The area behind the posterior gluteal line gives origin to the gluteus maximus.
  • The area between anterior and inferior posterior gluteal lines gives origin to gluteus medius.
  • The area between the anterior and inferior lines gives origin to the gluteus minimus.
  • The area below the inferior gluteal line gives origin to the reflected head of the rectus femoris.

Bones Of The Lower Limb Attachment of muscles on outer surface of right hip bone

Attachment of Muscles on the Inner Aspect (Sacropelvic Surface and Iliac Fossa) of the Ilium

  • The iliacus muscle arises from the upper 2/3rd of the iliac fossa.
  • The pelvic part of the sapropelic surface of the vilium above the obturator foramen gives origin to the obturator internus muscle.

Muscles Attached to the Anterior Border and Sciatic Notch of the Ilium.

  • The anterior superior iliac spine and an area below it give origin to the sartorius muscle.
  • The straight head of the rectus femoris arises from the anterior inferior iliac spine.
  • A small part of the piriformis arises from the upper border of the greater sciatic notch.

Pubis

Muscles Attached to the Pubic Bone

  • The adductor longus muscle arises from a rounded tendon from the anterior surface of the body of the pubis.
  • The origin of pyramidal is just above the origin of the adductor longus.
  • Note the attachments of gracilis, adductor brevis, and obturator externus on the anterior surface of the body (from medial to lateral).
  • These attachments also extend further downwards on the outer surface of the conjoined ischiopubic ramus.
  • The obturator internus arises from the pelvic surface of the body and the superior and inferior ramus of the pubic bone.
  • The pelvic (posterior) surface of the body gives origin to the anterior fibers of the levator ani.

Bones Of The Lower Limb Attachment of muscles on inner aspect of right hip bone

  • The pectineus arises from the pectineal surface of the superior ramus of the pubis.
  • Rectus abdominis arises from the pubic crest.

Ischium

Muscles Attached to Ischium

  • Note the origin of superior and inferior gemelli concerning lesser sciatic notch.
  • The quadratus fetnoris muscle arises from the femoral surface of the ischium.
  • The obturator extemus arises from the body and ramus of ischium close to the obturator foramen.
  • Posterior fibers of the levator ani and coccygeus muscles arise from the pelvic surface of the ischial spine.
  • The origin of muscles from the ischial tuberosity. The adductor magnus arises from the lower lateral part of the ischial tuberosity. The origin also extends on the outer surface of the ramus of ischium.
  • The semi-membranosus arises from the upper lateral part of the ischial tuberosity.

Bones Of The Lower Limb The origin of muscles from ischial tuberosity

  • The upper medial part of ischial tuberosity gives origin to the long head of the biceps fetnoris and Semitenditwsus.

Attachment of Ligaments and Fascia on the Hip Bone

  • The inguinal ligament is attached medially on the pubic tubercle and laterally on the anterior superior iliac spine.
  • The conjoined tendon is attached to the pubic crest and pectin pubis.
  • The lacunar ligament is attached to the pubic tubercle and pectin pubis.
  • The anterior wall of the rectus sheath is attached to the pubic crest.
  • The fascia lata is attached to the outer lip of the iliac crest, pubic crest, and lower border of the conjoined ischiopubic ramus.
  • The anterior and middle layer of thoraco lumbar fascia is attached to the iliac crest, anterior and posterior to the attachment of the quadratus lumborum muscle.
  • The superior and inferior fascia of the urogenital diaphragm are attached to the conjoined ischiopubic rami.
  • The acetabular labrum is attached to the margin of the acetabulum.

Bones Of The Lower Limb The attachment of inguinal ligament, pectineal liagment and lacunar liagement

  • The iliac tuberosity (on the sapropelic surface) gives attachment to the dorsal and interosseous sacroiliac ligament.
  • The posterosuperior and posteroinferior iliac spines and posterior border of the ilium give attachment to the upper end of the sacrotuberous ligament.
  • The lower end of this ligament is attached to the medial margin of the ischial tuberosity.
  • The sacrospinous ligament is attached to the ischial spine.

Blood Vessels and Nerves to the Hip Bone

  • The pudendal nerve, nerve to the obturator interims, and internal pudendal vessels lie about the posterior surface of the ischial spine.
  • The obturator vessels and nerve lie close to the inferior border of the superior ramus of the pubis (in the obturator canal).
  • The superior gluteal vessels and nerves concern the gluteal surface of the ilium.
  • The femoral surface of the body of the ischium is with the sciatic nerve and nerve to the quadratus femoris.

Ischium Ossification

The hip bone is organized by three primary centers. Many secondary centers appear at puberty and fuse with the rest of bone between 20 and 25 years of age (two secondary centers for iliac crest, two for acetabular cartilage, one for anterior inferior iliac spine, one for pubic tubercle, and one for pubic crest).

Bones Of The Lower Limb Attachment of sacrotuberous and sacrospinous ligaments. Note the relation of blood vessels and nerves

Bones Of The Lower Limb Inner(pelvic) Surface Of Left Hip Bone

Bones Of The Lower Limb External surface of pubis and ischium of right hip bone

Bones Of The Lower Limb Anterior aspect of Anterior Aspect of Upper end Of Right Femur

Bones Of The Lower Limb Posterior Aspect Of Upper End Of Right Femur

Bones Of The Lower Limb Ossification of hip bone

Bones Of The Lower Limb The anterior aspects of right femur

Clinical importance fractures

  • Fractures of the hip bone are not very common. They may occur due to roadside accidents or due to sports injuries.
  • The direct anteroposterior compression of the hip bone leads to a fracture of the pubic rami. Lateral compression may produce a fracture of the acetabulum.
  • Similarly, a fall on the feet from a roof may lead to a fracture of the superior margin of the acetabulum.
  • During sports, a sudden pull of muscles attached to anterior superior and inferior iliac spines, ischial tuberosity, and ischiopubic rami may lead to the tearing of these bony projections. These kinds of fractures are called avulsion fractures.
  • In this kind of fracture, a small part of the bone with a piece of tendon or ligament attached is torn away.

Femur

  • The femur is the bone of the thigh region. It is the longest, strongest, and heaviest bone in the body. The femur consists of a shaft, an upper end, and a lower end.
  • The upper end presents a rounded head, which articulates with the acetabulum of the hip bone to form a hip joint. The head is joined to the shaft by an elongated neck.
  • The lower end of the femur is expanded and presents two condyles, i.e., medial and lateral, which articulate with tibia and patella to form the knee joint.
  • The anterior surface of the shaft is smooth and convex forwards. There is the presence of a rough and thick vertical ridge (lined aspera) on the posterior aspect of the shaft.

Bones Of The Lower Limb The anterior aspects of right femur

Femur Side Determination

  • The rounded head is the upper end of the bone.

Bones Of The Lower Limb The posterior aspects of right femur

  • The head should be directed upwards, medially, and slightly forward.
  • The smooth convex surface of the shaft should be directed forward.

Femur Anatomical Position

The shaft of the femur is obliquely placed (the lower end of the femur is directed downwards and medially).

Because the upper ends of two femora are widely separated by two hip bones two knee joints are placed close to each other when a person stands in the anatomical position.

As the female pelvis is broader the knee joints are more closely placed in females as compared to males.

  • Keep the bone in such a way that the head faces upwards, medially, and slightly forwards.
  • The long axis of the shaft should be directed downwards and medially so that the two lower surfaces of both the femoral condyles lie in the same horizontal plane.

Bones Of The Lower Limb The Anatomical Postion of femur

Femur General Features

The Upper End

The proximal end of the femur consists of a rounded head, neck, and two trochanters (greater and lesser).

Femur Head

The head is like a ball, which forms about 2/3rd of a sphere. Near its middle, there is the presence of a pit for attachment of ligamentum teres.

Femur Neck

The neck connects the head to the shaft. The head and neck make an angle of about 126 degrees with the long axis of the body of the femur. The neck has a superior and an inferior border and an anterior and a posterior surface.

Femur Trochanters

Greater and lesser trochanters are two large elevations at the junction of the neck with the shaft. The greater trochanter is a large, laterally placed quadrilateral mass.

This trochanter presents three surfaces (anterior, medial, and lateral) and a superior and posterior border. The medial surface of the greater trochanter presents a deep depression called as trochanteric fossa. The lateral surface presents an oblique ridge that runs forward and downwards.

The lesser trochanter is a conical projection, directed medially and situated on the posteromedial surface at the neck-shaft The site where the neck joins the shaft, on the anterior aspect, is indicated by the presence of an intertrochanteric line.

This rough line runs between greater and lesser trochanters. On the posterior aspect, a similar but smoother ridge joins two trochanters.

This is known as the intertrochanteric crest, which marks the junction of the neck with the shaft posteriorly. The middle of the intertrochanteric crest presents a quadrate tubercle.

The Shaft

The shaft or body of the femur shows a slight bowing anteriorly. The shaft is narrowest in the middle but expanded towards the upper and lower ends.

Bones Of The Lower Limb Upper end of femur showing lesser trochanter sprial line and linea aspera

  • The shaft presents three surfaces (anterior, medial, and lateral) separated by three borders (medial, lateral, and posterior).
  • The medial and lateral borders are rounded and featureless.
  • The posterior border or linen aspera is a broad, rough vertical ridge.
  • As the linea aspera is broad in the middle part of the shaft it presents a medial lip, a lateral lip, and an intermediate area.
  • When the linea aspera is traced upwards its lateral lip continues as broad rough gluteal tuberosity and the medial lip continues as a narrow rough spiral line.
  • The upper end of gluteal tuberosity extends upto the greater trochanter.
  • There lies a small triangular surface (posterior surface) between the gluteal tuberosity and spiral line in the upper third of the shaft.
  • When the linea aspera is traced downwards its medial lip continues below as medial supracondylar line.
  • Similarly, the lateral lip of linea aspera continues below a lateral supracondylar line. The triangular surface between these two lines is called as popliteal surface.

Lower End

The lower expanded end of the femur consists of medial and lateral condyles, intercondylar fossa, and articular surfaces (tibial and patellar) for articulation with the tibia and patella.
Two condyles are joined together anteriorly but separated posteriorly by the intercondylar fossa or notch.

  • Both the condyles of the femur articulate with the corresponding condyles of the tibia and patella to form the knee joint.
  • Each condyle presents five surfaces, i.e., anterior, posterior, medial, lateral, and inferior.
  • The anterior surfaces of two condyles present an articular patellar surface. It articulates with the posterior surface of the patella.
  • The outer surface of both the condyles (medial surface of medial condyle and lateral surface of lateral condyle) is rough and convex.
  • The prominent bony points on the outer surfaces of both condyles are called epicondyles.
  • An adductor tubercle is present postero-superior to the medial epicondyle at the lower end of the medial supracondylar ridge.
  • The inner surface of both the condyles, i.e., the lateral surface of the medial condyle and the medial surface of the lateral condyle form the medial and lateral walls of the intercondylar fossa.
  • The inferior and posterior surfaces of both the condyles are articular and articulate with tibia. Anteriorly, the tibial articular surfaces of both condyles are continuous with the patellar surface.

Bones Of The Lower Limb Inferior surface of lower end showing medial and lateral epicondyles and petellar articular surface

Bones Of The Lower Limb Anterior aspect of lower end of right femur

Bones Of The Lower Limb Lateral view of lower end of right femur

Femur Particular Features

  • Muscles Attached to the Upper End of the Femur
  • The obturator interims and two Gemelli are inserted on the medial surface of the greater trochanter.
  • The obturator externus is attached into the trochanteric fossa.
  • The piriformis is inserted on the upper border of the greater trochanter.
  • The gluteus minimus is inserted on the anterior surface of the greater trochanter.
  • The gluteus medius is inserted on the lateral aspect of the greater trochanter.
  • The psoas major is inserted on the lesser trochanter.
  • The quadratus femoris is attached to the quadrate tubercle.

Bones Of The Lower Limb Anterior aspect of right femur showing attachment of muscles

Bones Of The Lower Limb The posterior aspects of right femur

Muscles Attached to the Shaft of the Femur

  • The iliacus and pectineus are inserted just below the lesser trochanter.
  • The insertion of pectineus lies between the gluteal tuberosity and the spiral line.
  • A part of the gluteus maximus is inserted on the gluteal tuberosity.
  • The vastus medialis has a linear origin, i.e., from the lower part of the intertrochanteric line, spiral line, the medial lip of linea aspera, and upper 2/3rd of the medial supracondylar line.
  • Similarly, the origin of vastus lateralis is also linear. It arises from the upper part of the intertrochanteric line, greater trochanter, lateral margin of the gluteal tuberosity, and lateral lip of linea aspera.

Bones Of The Lower Limb Attachment of muscles on linea aspera.

  • The vast intermediate originates from the anterior and lateral surfaces of the shaft.
  • Students should note the attachments of the following structures on the linea aspera, from medial to lateral side, with the help.
  • The vastus mediaiis on the medial lip, medial intermuscular septum, adductor brevis (above) adductor longus (below), adductor magnus, posterior intermuscular septum, short head of biceps femoris, lateral intermuscular septum and vastus lateralis.

Muscles attached to the lower end of the femur

  • The popliteus muscle takes its origin from the groove present below the lateral epicondyle.
  • The medial head of the gastrocnemius arises from the popliteal surface above the medial epicondyle.
  • The lateral head of the gastrocnemius arises from the lateral surface of the lateral condyle.
  • The lower part of the lateral supracondylar line gives origin to the plantaris.
  • The adductor magnus is inserted on the medial supracondylar line.
  • The tendon of the ischial part of the adductor magnus is attached to the adductor tubercle.

Attachments of Ligaments and Intermuscular Septa on the Femur A Few important ligaments and septa are described below:

  • The pit or fovea on the head of the femur gives attachment to the ligamentum teres.
  • The medial intermuscular septum is attached to the medial lip of linea aspera and the lateral septum is attached to the lateral lip.
  • The posterior intermuscular septum is attached to the intermediate area of linea aspera.
  • The posterior cruciate ligament is attached to the lateral surface of the medial condyle.
  • The anterior cruciate ligament is attached to the medial surface of the lateral condyle.

Blood Vessels Concerning the Bone

  • The femoral artery lies anterior to the head of the femur.
  • The popliteal artery lies on the popliteal surface of the bone.
  • Any major nerve is not directly related to the femur.

Femur Ossification

The femur ossifies by one primary and four secondary centers (three for the upper end and one for the lower end. The lower end is the growing end of the femur.

Bones Of The Lower Limb Relation of arteries on the posterior aspect of femur

Bones Of The Lower Limb Ossification of femur

Clinical importance

  • The secondary center for the lower end appears just before birth (ninth months of intrauterine life).
  • The presence of this center indicates that the fetus is mature (viable) enough to survive after birth.
  • The above fact is used as medicolegal evidence in case if a newborn infant found dead was capable of living at birth or not.
  • The fracture of the neck of the femur is common in old people, especially in females.
  • The fracture through the neck of the femur is also associated with the injury to blood vessels lying on the surface of the neck.
  • These vessels are responsible for the blood supply of the head. Rupture of these blood vessels leads to degeneration of the femoral head (avascular necrosis of the head).
  • Fracture of the femur between greater and lesser trochanter is also common in old persons.
  • Fracture of the shaft is usually a clue to direct injury as in vehicle accidents.
  • If the angle of inclination (the angle between the long axis of the body and the long axis of the neck) is reduced then the condition is called coxa vera.
  • If this angle is increased the condition is called coxa valga. The normal angle is about 125.

Bones Of The Lower Limb Coxa vera and coxa valga

Tibia

  • The skeleton of the leg is formed by two long bones, i.e., the tibia and fibula.
  • The tibia is the medial weight-bearing bone of the leg. It consists of an upper end and a lover end and a shaft or body. The upper end of the tibia is expanded and bears medial and lateral condyles.
  • These condyles articulate with the lower end of the femur to form the knee joint.
  • The lower end of the tibia on its medial aspect bears a downward projection called medial malleolus.
  • The shaft or the body of the bone bears a prominent sharp ridge known as an anterior border. The upper end of the anterior border bears a projection called tibial tuberosity.

Bones Of The Lower Limb Anterior aspect of right tibia

Bones Of The Lower Limb Anterior aspect of right tibia

Tibia Side Determination

  • The expanded upper end (bearing medial and lateral condyles) should be directed upwards.
  • The sharp and prominent anterior border and the tibial tuberosity should be placed anteriorly.
  • Medial malleolus at the lower end should face medially.

Tibia Anatomical Position

Bone should be kept vertically by holding it in the same hand, to the side it belongs.

Tibia General Features

Tibia Upper End

  • The upper end consists of medial and lateral condyles, an intercondylar area, and a tibial Shaft tuberosity.
  • The upper surface of the medial and lateral condyles is articular.
  • The articular surface of the medial condyle is oval and large while that of the lateral condyle is small and circular.
  • A non-articular rough area is placed between two articular surfaces. This is known as the intercondylar area.
  • There is the presence of an elevation in the middle of the intercondylar area (intercondy- lar eminence). This eminence is formed by two tubercles, i.e., medial and lateral intercondylar tubercles.
  • The posterior surface of the medial condyle is deeply grooved.
  • The posterolateral surface of the lateral condyle bears a circular articular facet for the head of the fibula. This articulation is known as the superior tibio-fibular joint.
  • The anterior surface of both condyles bears a triangular area. The apex of this triangle is directed downwards and there lies a rough projection called tibial tuberosity.

Bones Of The Lower Limb Superior surface of medial and lateral condyles of right tibia

  • The shaft of the tibia is triangular in cross-section, hence presenting three borders (anterior, medial, and lateral or interosseous) and three surfaces (medial, lateral, and posterior).
  • The anterior border extends from the tibial tuberosity to the anterior margin of the medial malleolus. It is a sharp, subcutaneous border.
  • The medial border extends from the medial condyle to the posterior border of the medial malleolus.
  • The lateral or interosseous border extends from the lateral condyle to the anterior border of the fibular notch at the lower end of the tibia.
  • The lateral surface lies between the anterior and interosseous borders.
  • The medial surface lies between the anterior and medial borders. This surface is smooth because it is subcutaneous.
  • The posterior surface lies between medial and lateral borders. This surface is marked by the presence of an oblique sole line. Thus posterior surface presents a triangular area above the sole line and a medial and a lateral area below the sole line

Tibia Lower End

  • This end of the tibia is much less expanded as compared to the upper end. This end projects downwards and medially as the medial malleolus.
  • The posterior surface of the malleolus presents a groove. The lateral surface of the lower end shows a triangular area (fibular notch) for articulation with the fibula to form an inferior tibiofibular joint.
  • The inferior surface of the lower end including the medial malleolus is articular and articulates with the body of the talus to form the ankle joint.

Bones Of The Lower Limb Posterior surface of the upper end of left tibia

Bones Of The Lower Limb Superior surface of condyle of right tibia

Tibia Particular Features

Attachment of Muscles on Tibia

  • The tibial tuberosity gives attachment to the lignmentum patellae (tendon of quadriceps femoris).
  • The semi-membranosus is inserted in the horizontal groove on the posterior surface of the medial condyle.
  • The upper part of the media surface receives the insertion of three muscles from before backward, i.e., sartorius, gracilis, and semitendinosus.
  • The upper 2/3rd of the lateral surface gives origin to the tibialis anterior.
  • On the posterior surface of the bone, the popliteus is inserted above the sole line.

Bones Of The Lower Limb Attachment of muscle on anterior aspect of tibia

Bones Of The Lower Limb Attachment Of Muscles On Posterior Aspect Of Right Tibia

  • The sole line itself gives origin to the soleus muscle.
  • The medial area below the soleal line, on the posterior surface, gives origin to the flexor digitorum longus. While the lateral area gives origin to the tibialis posterior.

Attachment of Ligaments on the Tibia

  • The anterior and posterior parts of the intercondylar area give attachment to the following structures from before backward anterior horn of medial meniscus, anterior cruciate ligament, anterior horn of lateral meniscus, posterior horn of lateral meniscus, posterior horn of medial meniscus, and posterior cruciate ligament.
  • The lower end of the iliotibial tract is attached to a small triangular area on the anterior surface of the lateral condyle.

Bones Of The Lower Limb Attachment on the superior surface of medial and lateral condyles of right tibia

Bones Of The Lower Limb Structures attached on the anterior aspect of the upper end of tibia

  • The tibial collateral ligament is attached to the medial surface near the upper end of the medial border.
  • The interosseous or lateral border gives attachment to interosseous membrane.
  • The fibular notch gives attachment to the interosseous tibiofibular ligament.

Tendons, Blood Vessels, and Nerves Related to Tibia

Following tendons, vessels, and nerves are related on the anterior aspect of the lower end (from medial to lateral): tibialis anterior, extensor hallucis longus, anterior tibial vessels, deep peroneal nerve, extensor digitorum longus, and peroneus tertius.

Bones Of The Lower Limb Anterior aspect of lower end of left tibia Showing relations of tendons vessels and nerve

Following tendons, vessels, and nerves are related to the posterior aspect of the lower end of the tibia (from medial to lateral side): tibialis posterior, flexor digitorum longus, posterior tibial vessels, posterior tibial nerve, and flexor hallucis longus.

Bones Of The Lower Limb Posterior Aspect Of Lower End Showing Relation Of Tendons And Vessels

Tibia Ossification

Tibia ossifies from three centers, i.e., one primary center for the shaft and two secondary centers one each for the upper and lower end. The upper end is the growing end of the tibia.

Bones Of The Lower Limb The Ossification Of Tibia

Tibia Clinical importance

  • The most common site for the fracture of the tibia is at the junction of the middle and lower 1/3rd.
  • This is because the tibia is narrowest at this point. The fracture of the lower 1/3rd of the tibia is difficult to heal as this part of the tibia is devoid of muscle attachment and the periosteal blood supply is poor.
  • The tibia is subjected to severe torsion during various sports, which may lead to diagonal fracture of the tibial body. The body of the tibia is also the most common site for compound fracture.
  • In a compound fracture, blood vessels and skin are torn by the fractured end of the tibia. This is because the tibia is subcutaneous hence skin is easily torn.

Fibula

The fibula is the lateral bone of the leg. Though the slender fibula has no weight-bearing function, but gives attachment to muscles and its lower end (lateral malleolus) takes part in the formation of the ankle joint.

The fibula has an upper end, a lower end, and an intervening shaft.

The upper rounded end is also known as the head. The head bears a styloid process and an oval articular surface for articulation with the lateral condyle of the tibia.

The lower end of the fibula is expanded anteroposteriorly to form the lateral malleolus.

The medial surface of the lower end presents a triangular articular surface front and a depression, the malleolar fossa, just posteroinferior to the triangular articular surface.

Fibula Side Determination

The side of the fibula can be determined just by looking at its lower end Keep the lower end (lateral malleolus) downwards.

Bones Of The Lower Limb General Features Of Right Fibula As Seen From Front

Bones Of The Lower Limb Right Fibula As Seen From Behind

  • The triangular articular surface of the lateral malleolus should face medially.
  • The malleolar fossa should face downwards, backward, and medially.

Fibula Anatomical Position

Once you have determined the side of the bone then hold the bone vertically in the hand of the same side to which it belongs.

Fibula General Features

Upper End or Head

  • It has a pointed apex known as the styloid process.
  • The superior surface of the upper end bears an oval articular facet.
  • The neck is the constricted part of the bone just below the head.

Bones Of The Lower Limb Medical Surface At The Lower End Of Fibula

Lower The End lateral Lateral malleolus

  • The malleolus presents lateral, medial, and posterior surfaces and an anterior border.
  • The lateral surface is convex, triangular, and continuous above with anterior border. It is a subcutaneous surface.
  • The medial surface bears a triangular articular facet for the articulation with the talus.
  • Behind the facet there is a rough depression called a malleolar fossa.
  • The posterior surface presents a groove for the tendon.

Shaft

The shaft of the fibula has three borders (anterior, interosseous, and posterior) and three surfaces (medial, lateral, and posterior).

(As the borders and surfaces of fibula are difficult to identify, take the help of your teacher. Hold the bone in the anatomical position and trace these borders as described below).

Anterior Border

It begins just below the anterior surface of the head. Trace this sharp border downwards near the lower end of the bone this border splits to enclose a subcutaneous triangular surface on the lateral aspect of the lateral malleolus.

Interosseous Border

  • This border is very close and medial to the anterior border.
  • It begins just below the anterior surface of the head. When traced downwards it passes medially to end in a rough triangular surface on the medial surface of the lower end.

Posterior Borders

It extends from the posterior aspect of the head to the lateral lip of a groove on the posterior aspect of the lateral malleolus.

Medial (Extensor) Surface It is a very narrow surface and lies between anterior and interosseous borders. It is also known as the anterior surface.

Lateral (Peroneal) Surface It lies between anterior and posterior borders. At the lower end, this surface becomes continuous with the posterior aspect of the lateral malleolus

Posterior (Flexor) Surface

It lies between the interosseous and the posterior border. This surface in its upper 2/3rd is divided into medial and lateral parts by a sharp vertical ridge called as medial crest, of

Attachment of Intermuscular Septum

  • The anterior and posterior borders give attachment to the anterior and posterior intermuscular septum.
  • The interosseous border gives attachment to the interosseous membrane.
  • The medial crest gives attachment to the transverse intermuscular septum.

Attachment of Muscles on Fibula

The medial or extensor surface gives origin to three muscles, i.e., the extensor digitorum.

Bones Of The Lower Limb Attachment Of Muscleus On Anterior Aspect of fibula

Bones Of The Lower Limb Attachment of muscles on posterior aspect of fibula

  • longus (from its upper 3/4th surface), extensor hallucis longus (from its middle 2/ 4th), and peroneus tertius from the lower 1 /4th below the origin of extensor digitorum longus.
  • The posterior surface gives origin to the tibialis posterior from the anterior concave surface lying anterior to the medial crest.
  • The surface posterior to the medial crest gives origin to the soleus in the upper 3/4th and flexor hallucis longus from its lower 3/4th.
  • The lateral surface gives origin to the peroneus longus from its upper 3/4th and peroneus brevis from its lower 2/3rd. In the middle third of this surface peroneus brevis lies in front of peroneus longus.
  • The lower end of the fibula is devoid of muscular attachments

Tendons and Nerves with Fibula

  • The tendon of the peroneus longus and brevis are related to the posterior surface of the lateral malleolus.
  • The common peroneal nerve is related to the lateral aspect of the neck of the fibula.

Fibula Ossification

The fibula is organized by three centers. One primary center for the shaft and two secondary centers, one each for the upper and lower ends.

Bones Of The Lower Limb Posterior surface at the lower end of fibula

Bones Of The Lower Limb Ossification of fibula

Bones Of The Lower Limb Medical Aspect Of Lower End Of Fibula

Bones Of The Lower Limb Lateral Aspect Of The Articulated Right foot

Bones Of The Lower Limb Right Superior Dorsal Aspect Of The Right Articulated Foot

Bones Of The Lower Limb Plantar aspect of the right articulated foot

The fibula is an exception to the law of “growing end” (i.e., the secondary center, which appears first is also the first to fuse with the bone formed by the primary center).

Bones Of The Foot

  • The bones of the foot consist of tarsus, metatarsus, and phalanges. Each foot consists of 7 tarsal, 5 metatarsal, and 14 phalanges, which are arranged proximodistally.
  • Though we shall study the features of individual bones of the foot students are advised to study an articulated skeleton of the foot to see the arrangement of these bones with each other.
  • In my opinion, undergraduate students, need not study every bone of the foot in detail. Therefore, only two tarsal bones (calcaneus and talus) are described in detail.

Tarsal Bones

  • These are short bones, which form the posterior half of the foot. They are arranged in three rows. The proximal row consists of the talus and calcaneus.
  • The calcaneus is the largest tarsal bone and forms the heel of the foot. Placed above the anterior 2/3rd of the calcaneus.

Bones Of The Lower Limb Skeleton of foot as seen from dorsal aspect

Bones Of The Lower Limb Skeleton of foot as seen from plantar aspect

There is another tarsal bone called a talus. The talus articulates with the lower end of the tibia and fibula to form the ankle joint. Anterior to the calcaneus and talus, the middle row is formed by navicular and cuboid bones.

The proximal end of the navicular bone articulates with the head of the talus and is placed medially.

The cuboid bone is placed laterally and articulates proximally with the calcaneus.

The distal surface of the navicular bone articulates with the other three tarsal bones, i.e., medial, intermediate, and lateral cuneiforms.

Bones Of The Lower Limb Skeleton of foot as seen from medial aspect

Bones Of The Lower Limb Attachment of ligaments on the plantar Aspect Of Foot, as seen from lateral aspect

Bones Of The Lower Limb The dorsal surface of talus

Talus

The talus has a body, neck, and head. It is situated on the calcaneus.

Body

  • The superior surface of the body is articular and bears a large trochlear articular surface for articulation with the lower end of the tibia.
  • The medial surface of the body shows a comma-shaped articular facet for articulation with the medial malleolus. While the lateral surface bears a large triangular facet for articulation with the lateral malleolus of the fibula.
  • The inferior surface of the body of the talus presents a concave facet, which articulates with the convex facet on the upper surface of the middle third of the calcaneus to form the talar joint.
  • The posterior surface is narrow and has a groove for a tendon. This groove has a prominent lateral tubercle and a less prominent medial tubercle.

Neck

The neck of the talus projects forward and medially from the body of the talus. It is nonarticular and bears a groove (sulcus tali) on its inferior surface.

Head

The rounded head is directed forwards, medially, and slightly downwards. The head bears an extensive convex articular surface, which articulates anteriorly with the navicular bone and below with the upper surface of the sustentaculum tali of the calcaneus and spring ligament.

The talus is the only tarsal bone that has no muscular or tendinous attachments. The sulcus tali gives attachment to the interosseous talocalcanean ligament.

Bones Of The Lower Limb The plantar surface of talus

Talus Side Determination

  • The rounded articular head should be directed forward.
  • The large trochlear articular surface should face upward.
  • The large triangular articular surface placed on the side of the body should face laterally.

Talus Anatomical Position

Hold the bone in such a way that the head is directed forwards, medially, and slightly downwards.

Calcaneus

The calcaneus is the largest and strongest tarsal bone of the foot. It forms the heel and is located below the talus.

It articulates superiorly with the talus and anteriorly with the cuboid bone. The calcaneus has six surfaces.

The anterior surface is articular and saddle in shape. It articulates with the cuboid bone.

The posterior surface is non-articular and roughing its middle part for the attachment of tendocalcaneus.

The medial surface is concave and bears a shelflike projection called sustentaculum tali.

The lateral surface of the calcaneus is flat and bears a peroneal tubercle.

The plantar or inferior surface of the calcaneus is rough and shows a large prominence on its posterior part called as calcaneal tuberosity.

The calcaneal tuberosity presents medial and lateral tubercles. The anterior part of the plantar surface bears an anterior tubercle.

Bones Of The Lower Limb The dorsal surface of calcaneous

Bones Of The Lower Limb The plantar surface of calcaneous

The dorsal or superior surface is partly articular and partly non-articular. It bears three articular facets (anterior, middle, and posterior facets) for articulation with the corresponding facets on the inferior surface of the talus.

There is the presence of a deep groove between the middle and posterior facets, sulcus calcanei. The sulcus calcanei and sulcus tarsi, in an articulated foot, form sinus tarsi.

Calcaneus Side Determination

  • The anterior articular surface should face anteriorly.
  • The superior surface bearing three articular facets should face upward.
  • The sustentaculum tali projects medially.

Calcaneus Anatomical Position

Hold the bone in such a way that the articular area for the cuboid should face forward and laterally with a slight upward inclination.

Navicular

The navicular bone is boat-shaped. It articulates distally with the head of the talus and proximally with three cuneiforms. The medial surface of the bone bears a navicular tuberosity.

Cuboid

It is the lateral bone extending in the distal row of the tarsus. It is approximately cubical. Proximally it articulates with calcaneus and distally with the 4th and 5th metatarsals.

On the lateral and inferior aspect, it bears a groove for the tendon of the peroneus longus. On this aspect, behind the groove, there is the presence of tuberosity.

The medial surface of the cuboid has articular facets for lateral cuneiform and navicular bone.

Cuneiform Bones

These are called medial, intermediate, and lateral cuneiforms. These bones articulate with the navicular proximally and with the bases of the 1st, 2nd, and 3rd metatarsals distally.

All these bones articulate with each other. The lateral surface of lateral cuneiform also articulates with the cuboid.

The metatarsal bones

  • The metatarsals are classified as miniature long bones. The five metatarsal bones are numbered from medial to lateral side, i.e., 1st, 2nd, etc. The first metatarsal is the shortest and strongest as compared to the others.
  • The second metatarsal is the longest. Each metatarsal has a proximally placed base, distally placed head, and intervening body. The heads of metatarsals are rounded and articulate with the proximal phalanges.
  • The base of each metatarsal is large as compared to its head and presents five surfaces (medial, lateral, dorsal, plantar, and proximal).
  • The base of 5th metatarsal has a large tuberosity for the insertion of the tendon of the peroneus brevis.

Phalanges

  • Similar to the metatarsals, phalanges are also classified as miniature long bones. The first toe has two phalanges (proximal and distal).
  • The lateral four toes have three phalanges each, i.e., proximal, middle, and distal. Each phalanx consists of a proximally placed base, a distally placed head, and an intervening body.
  • The first toe consists of two phalanges and has only one interphalangeal joint. While the rest of the toes have proximal and distal interphalangeal joints.

Bones Of The Lower Limb The second matatarsal of left side

Bones Of The Lower Limb Differences Between Metarsals And Metacarpals

Particular Features Of The Bones Of The Foot

  • The peroneus brevis is inserted on the lateral aspect of the base of the fifth metatarsal bone.
  • The peroneus tertius is attached to the dorsal aspect of the base of the fifth metatarsal.
  • The extens or digitorum longus is attached to the base of the middle and distal phalanges of the lateral four toes.
  • The extensor hallucis longus is inserted on the base of the distal phalanx of the great toe.
  • The tendocal caneous is inserted in the middle of the posterior surface of the calcaneus.

Bones Of The Lower Limb Insertion of leg muscles on the dorsal aspect of right foot

Attachment of Muscles on the Plantar Aspect of the Bones of Foot

  • The flexor hallucis longus is inserted into the base of the distal phalanx of the great toe.
  • The flex or digitorum longus is inserted into the plantar surface of the bases of the distal phalanges of lateral four digits.
  • The peroneus longus muscle is inserted at the base of the first metatarsal and on the lateral aspect of the medial cuneiform bone.
  • The tibialis anterior is inserted into the medial cuneiform and base of the first metatarsal on the medial and plantar aspects.
  • The tendon of the tibialis posterior has very extensive insertion. It is mainly inserted into the tuberosity of the navicular bone and medial cuneiform.
  • This tendon also sends slips to all other tarsal bones (except the talus) and bases of the 2nd, 3rd, and 4th metatarsals.
  • Origin and Insertion of the Intrinsic Muscles of the Foot The dorsal aspect gives origin to the extensor digitorum brevis.

On the plantar surface, many intrinsic muscles are attached (flexor digitorum brevis, abductor digit minim abductor hallucis, flexor digitorum accessories, flexor hallucis brevis, adductor hallucis, and flexor digit minimi brevis).

Students should learn the origin and insertion of all these muscles with the help of The origin and insertion of plantar interossei shown in the dorsal interossei.

Attachment of Ligaments on the Bones of the Foot

  • The bones of the foot give attachment to many ligaments. A few important ligaments are described here:
  • The interosseous talocalcaneal ligament is attached between the sulcus tali of talus and sulcus calcanei of calcaneus.
  • The spring ligament (plantar calcaneonavicular ligament) is attached to the anterior margin of sustentaculum tali of the calcaneus and the plantar surface of the navicular bone.
  • On the plantar surface, the long plantar ligament is attached posteriorly to the tuberosity of the calcaneus and anteriorly to the cuboid bone and bases of the 2nd, 3rd, and 4th metatarsal bones.

Bones Of The Lower Limb Attachment of muscles on plantar aspect of right foot

Bones Of The Lower Limb Origin and insertion of dorsal interossei

Bones Of The Lower Limb Attachment of ligaments on the plantar aspect of foot

Bones Of The Lower Limb Attachment of ligaments on the plantar Aspect Of Foot, as seen from lateral aspect

  • The short plantar ligament is proximally attached to the anterior tubercle of the calcaneus and distally on the cuboid.
  • The groove on the posterior aspect of the talus is related to the tendon of flexor hallucis longus.

Ossification

Tarsal Bones

Calcaneus is classified by one primary center and one secondary center. All other tarsal bones ossify by one center only. The ossification of metatarsal and phalanges.

Patella

The patella is also known as the kneecap as it lies in front of the knee joint. It is a small triangular bone present in the tendon of the quadriceps femoris.

The patella is not a true bone as it is devoid of periosteum, hence it is classified as a sesamoid bone.

The patella has an apex, a base, medial and lateral borders, and an anterior and a posterior surface. The base forms the upper border of the bone.

The apex is directed downwards. The anterior surface is rough and subcutaneous while the posterior surface is mostly articular.

The articular surface is divided into a smaller medial and a large lateral surface by a vertical ridge. These surfaces articulate with the corresponding surfaces on the femoral condyles.

Patella Side Determination

  • The apex of the patella should be directed downwards.
  • The smooth articular surface should face posteriorly.
  • The larger lateral part of the articular area should lie on the lateral side. The anterior surface is rough (presents several longitudinal ridges). The base, medial, and lateral borders give attachments to many muscles. The posterior surface is mostly articular.

Only a small portion near the apex is rough and gives attachment to the ligamentum patellae. The articular surface is divided into a large lateral and a small medial articular area by a vertical ridge.

Bones Of The Lower Limb Ossification of bones of foot

Bones Of The Lower Limb The anterior surface of right patella

Bones Of The Lower Limb The posterior (articular) surface of right patella

Bones Of The Lower Limb The Attachment Of Patella

These articular surfaces come in contact with the reciprocal patellar articular surface of the femur, i.e., the larger lateral area of the patella with lateral femoral condyle and medial area with medial condyle.

The medial articular area is further separated by a vertical ridge from the most medial narrow strip, which comes in contact with the medial condyle of the femur during full flexion.

As the patella moves downwards when the knee is flexed, its articular areas move on the articular areas at the lower end of the femur.

The various articular areas come in contact with the femur (from extension to full flexion).

Bones Of The Lower Limb Various articular areas coming in contact with Femur During Extension And Flexion

Patella Ossification

The patella is cartilaginous up to three years of age. Several ossification centers appear in the patella between 3 to 6 years of age. These centers unite with each other and complete the ossification.

Bones Of The Lower Limb Diagrammatic represention of the force transmission through the talus

Autonomic Nervous System Functions Notes

Autonomic Nervous System

The autonomic nervous system controls and coordinates the internal environment of the body. This system has two divisions:

  1. Sympathetic
  2. Parasympathetic

Both these divisions are complementary to each other. They function in coordination and adjust the body unconsciously to maintain the internal environment.

Most organs of our body receive innervations from both sympathetic and parasympathetic fibers. In general, a nerve impulse from one division stimulates the organ to increase the activity while the other will have the opposite action, i.e. decreases the activity.

For example, stimulation of sympathetic nerves increases the heart rate while stimulation of parasympathetic innervations decreases the heart rate.

The ANS consists of both afferent (sensory) and efferent (Motor) components and an integration center.

Autonomic Sensory (Visceral Afferent) Component The sensations of the autonomic system are transmitted from the viscera to the CNS through somatosensory fibers.

The cell bodies of sensory neurons are located in the dorsal root ganglion of spinal nerves and the sensory ganglia of some cranial nerves.

Somatosensory neurons are also responsible for visceromotor reflex activities. Though these sensations hardly reach the level of consciousness, the sensations of nausea and pain in
the heart is perceived.

Automomic Nervous System Pathway of visceral reflex.

Automomic Nervous System Visceral reflexes from Stomach, heart, colon

Automomic Nervous System Visceral reflexes from Stomach, heart, colon.

Automomic Nervous System Visceral reflexes from Stomach, heart, colon..

Integration and Control of the Autonomic Nervous System. The autonomic activities are integrated at higher levels. These centers are situated in the reticular formation of the brainstem, hypothalamus, limbic cortex, and prefrontal cortex.

The hypothalamus is considered the higher center (control and integration) of ANS. It controls both sympathetic and parasympathetic divisions of ANS.

The neurons of sympathetic and parasympathetic nuclei in the brainstem and spinal cord are connected with the nuclei of the hypothalamus through the reticular formation.

Autonomic Motor (Visceral Efferent) Component. The autonomic activities regulate body temperature, heart rate, respiration, blood pressure, gastrointestinal motility, and secretion from glands.

Thus, ANS consists of motor (efferent) fibers that innervate smooth muscle, cardiac muscle, and glands.

The effector cells of different organ systems are not under voluntary control; they work mostly at an unconscious level.

Both sympathetic and parasympathetic motor pathways consist of two motor neurons that conduct the impulses from the CNS to the effector organ.

The cell bodies of the first motor neurons are located in the grey matter of the CNS (brain and spinal cord). These are called preganglionic or presynaptic neurons.

The preganglionic neurons send their myelinated axonal processes to synapse with the second motor neurons in the pathway.

The axons of presynaptic neurons come out of the CNS as part of either the spinal or the cranial nerve.

The cell bodies of second motor neurons are located in the autonomic ganglia outside the CNS.

These are called post-synaptic or post-ganglionic neurons because presynaptic neurons make synaptic contact with them.

The axons of post-synaptic neurons are unmyelinated and terminate on the effector organs (smooth muscle, glands, or cardiac muscle).

Sympathetic Division Of Autonomic Nervous System

The sympathetic division of the autonomic nervous system is also called thoracolumbar outflow as the preganglionic nerve cells are situated in the thoracic and upper lumbar segments of the spinal cord.

The cell bodies of presynaptic neurons of the sympathetic division of ANS are located in the lateral grey column (horn) of the spinal cord between the T1 and L2 spinal segments.

The cell bodies of postsynaptic neurons are located in two groups:

  1. Paravertebral ganglion (sympathetic trunk ganglia) and
  2. Pacvcrtebral ganglion.
  3. Sympathetic trunk ganglia lie in a vertical row on either side of the vertebral column extending from the base of the skull to the coccyx.
  4. On the other hand, prevertebral ganglia are situated anterior to the vertebrae and close to the origin of the main branches of the abdominal aorta.
  5. Examples of prevertebral ganglia are celiac ganglion, superior mesenteric ganglion, and inferior mesenteric ganglion close to the beginning of arteries of the same name.
  6. The axons of presynaptic neurons leave the spinal cord through ventral roots and enter the ventral rami of spinal nerves (T1 to L2).
  7. These axons are myelinated fibers. They leave the ventral ramus as a slender branch called white ramus communicantes and enter the sympathetic trunk.
  8. The presynaptic fibers of white ramus communicantes, after entering the sympathetic trunk, may synapse with the postsynaptic neurons present in the sympathetic ganglion at the same level.
  9. These fibers may also ascend or descend in the sympathetic trunk for a few levels before forming synaptic connections.
  10. It may also happen that these fibers pass through the sympathetic trunk without synapsing and join the splanchnic nerve to reach the prevertebral ganglia and synapse with the post-ganglionic neurons there.

The splanchnic nerves of the thorax are as follows

  1. Greater (T5 to T9)
  2. Lesser (T10 and Til)
  3. Least (T12)

The splanchnic nerves of the thorax are greater (T5 to T9), lesser (T10 and Til), and least (T12) while lumbar splanchnic nerves take origin from LI to L4 sympathetic ganglia.

The post-synaptic neurons of sympathetic ganglia send their axons (post-synaptic sympathetic fibers) to the adjacent ventral rami of spinal nerves.

These axons are non-myelinated and are called gray rami communicantes. From the ventral rami, they go to all branches of the spinal nerve including the dorsal rami.

The post-ganglionic fibers from paravertebral sympathetic ganglia (sympathetic trunk ganglia) supply the blood vessels (vasomotor), sweat glands, and smooth muscle of hair follicles (erector pili) in the skin of limbs and body wall.

Automomic Nervous System Sympathetic nervous system.2

The post-ganglionic fibers from T1 to T5 supply thoracic viscera (heart, lung, trachea, and esophagus) via cardiac and pulmonary plexus.

The post-ganglionic fibers from prevertebral sympathetic ganglia (coeliac, superior and inferior mesenteric, and hypogastric ganglia, and plexuses) supply the abdominal and pelvic viscera (liver, kidney, stomach, intestine, rectum, colon, urinary bladder, genital organ, etc.)

The post-ganglionic fibers from the prevertebral sympathetic ganglia follow the course of various arteries.

(Students should note that the prevertebral ganglia consist of post-ganglionic sympathetic neurons only. However; these plexuses consist of both sympathetic and parasympathetic fibres.)

Automomic Nervous System Location of prevertebral ganglia and plexuses.

The sympathetic nervous activities are widely diffused activities that affect the whole body. The sympathetic reaction deals with emergencies or emotional stress.

The sympathetic reaction leads to the dilatation of the pupil, pale face (due to vasoconstriction in the skin), dry mouth, increased heart rate, and raised blood pressure.

The peristaltic movements of the intestine are suppressed and sphincters are closed. The blood vessels of skeletal muscles, heart, and brain dilate to supply more blood to these vital organs.

Parasympathetic Division Of Autonomic Nervous System

The parasympathetic division of ANS is also known as craniosacral outflow as preganglionic neurons are situated in the brain and sacral segment of the spinal cord.

Cranial outflow: The cell bodies of the cranial part of parasympathetic preganglionic neurons are situated in the brain and axons come out along with cranial nerves 3, 7, 9, and 10.

Sacral outflow: The sacral parts of preganglionic neurons are situated in the lateral grey column (horn) of spinal cord segments S2 to S4.

Their axons come out of the spinal cord through the ventral rami. The fibers from ventral rami then travel into pelvic splanchnic nerves.

The axons of pre-ganglionic neurons are very long, as they reach up to the effector organs. Close to the organs or within the substance of the organ, there is the presence of ganglia called terminal ganglia.

The terminal ganglia consist of post-synaptic neurons. Pre-synaptic axons form synaptic contacts with these neurons.

The terminal ganglia consist of post-synaptic neurons. Pre-synaptic axons form synaptic contacts with these post-synaptic neurons.

As the terminal ganglia are close to the organ supplied by the parasympathetic nerve, the axons of post-synaptic neurons are very short. They innervate the smooth muscles and glands in the wall of an organ.

The terminal ganglia associated with cranial outflow are ciliary (3 cranial nerve), pterygopalatine ganglia, submandibular ganglia (4 cranial nerve), and otic ganglia (9 cranial nerve).

The post-ganglionic fibers from these ganglia supply the eye, salivary glands, and other structures of the head and neck.

The pre-ganglionic parasympathetic fibers in the vagus nerve extend to many terminal ganglia in the thorax and abdomen. The post-ganglionic fibers supply the heart and lungs in the thorax (through cardiac and pulmonary plexuses). They supply the liver, gall bladder, stomach pancreas, small intestine, and part of the large intestine pancreas, small intestine, and part of the large intestine in the abdomen (through coeliac and superior mesenteric plexuses).

The postganglionic fibers from sacral outflow supply smooth muscle and glands in the wall of the colon, ureter, urinary bladder, and reproductive organs (through the hypogastric plexus).

Automomic Nervous System Sympathetic fibres relaying in paravertebral ganglia (sympathetic chain) and prevertebral ganglion

Automomic Nervous System Sympathetic Segmental Supply

Automomic Nervous System Sympathetic innervation through lumbar and sacral sympathetic trunks

Sympathetic And Parasympathetic Systems A Comparison

Most of the organs in the body receive both types of motor innervations (sympathetic and parasympathetic). These two types of motor innervations usually have opposite ctions (antagonistic); that is, if one type of innervation increases the activity (excitation) of viscera, then the other type will decrease (inhibition) the activity.

For example, sympathetic stimulation leads to decreased mobility of the intestine and contraction of sphincters. On the other hand, parasympathetic stimulation leads to increased motility of the intestine and relaxation of sphincters.

Sympathetic overactivity causes dilatation of the pupil while parasympathetic overactivity leads to its constriction.

In parasympathetic nerves, the neurotransmitter at pre- and post-synaptic nerve terminals is acetylcholine.

Acetylcholine is liberated at the sympathetic preganglionic nerve terminals while norepinephrine is liberated at postganglionic nerve terminals.

Automomic Nervous System Parasympathetic nervous system

The autonomic innervations of some important organs of the body are described in brief in the following text

1. Eyeball

  • Sympathetic innervation—from the Tl spinal cord segment
  • Parasympathetic innervation—from the Edinger- Westphal nucleus
  • Stimulation of sympathetic innervation causes dilatation of the pupil and relaxation of ciliary muscles.
  • Stimulation of parasympathetic innervation causes constriction of pupil and ciliary muscle.
  • Horner’s syndrome (which occurs due to deinnervations of sympathetic nerves of the head and neck) has the following characteristics: Constriction of a pupil, partial ptosis, absence of secretion on the face, flushing of the face, and enophthalmos.

2. Submandibular and sublingual salivary glands

  • Sympathetic innervation—from Tl and T2 spinal segments
  • Parasympathetic innervation—from the superior salivatory nucleus of the facial nerve

3. Lacrimal gland

  • Sympathetic innervation—from Tl and T2 spinal segments
  • Parasympathetic innervation—from the lacrimatory nucleus of the facial nerve.

Automomic Nervous System Comparison Between Sympathetic And Parasympathetic Motor Innervotions

Automomic Nervous System Morphological Differences Between Sympathetic and Parasympathetic Nervous Systems

4. Parotid gland

  • Sympathetic innervation—from T1 and T2 spinal segments
  • Parasympathetic innervation—from the inferior salivatory nucleus of the glossopharyngeal nerve

5. Heart

  • Sympathetic innervation—from T1 to T5 spinal segments
  • Parasympathetic innervation—from the dorsal nucleus of the vagus nerve.

Automomic Nervous System Sympathetic and parasympathetic fibres innervating the iris

Automomic Nervous System Sympathetic and parasympathetic innervations of heart

The pain of a heart attack is felt over the middle of the sternum, left shoulder, jaw, and medial aspect of the left arm.

This is because these areas are supplied by the same segments of the spinal coral as the heart (T1 to T5).

6. Lungs

  • Sympathetic innervation—from T2 to T5 spinal segments
  • The pain of a heart attack is felt over the middle of the sternum, left shoulder, jaw, and medial aspect of the left arm.
  • This is because these areas are supplied by the same segments of the spinal coral as the heart (T1 to T5).

7. Gastrointestinal tract

  • Sympathetic innervation—from T5 to L2 spinal segments
  • Parasympathetic innervation—from the dorsal nucleus of the vagus and from the S2 to S4 spinal segment

Automomic Nervous System Effects Of Sympathetic And Parasympathetic Sitmulation On Different Organs

Automomic Nervous System Autonomic innervations of the urinary bladder.

8. Urinary bladder

  • Sympathetic innervation—from T10 to L2 spinal segments
  • Parasympathetic innervation—from S2 to S4 spinal segments
  • Sensory innervation—from T10 to L2 and S2 to S4

9. Arteries of the upper limb

  • Sympathetic innervation—from T2 to T8
  • Arteries of the lower limb
  • Sympathetic innervation-from T10 to L2 spinal cord segments
  • Autonomic innervations for the erection of the penis
  • Parasympathetic innervation—S2 to S4 spinal segments
  • Autonomic innervations for ejaculation from the penis
  • Sympathetic innervations from the LI segment.

Localisation Of Visceral Pain

Viscera are usually insensitive to touch, heat, and cutting (cutting of the intestine in a conscious person does not elicit visceral pain).

But if receptors are stimulated in large areas (diffuse stimulation) due to inadequate blood supply, collection of metabolites, distension (stretch), and spasm, then visceral pain can be very severe. When the kidney stone obstructs and distends the ureter, it causes severe pain.

The visceral pain is poorly localized and dull because receptors are stimulated in a large area. The pain may be felt in the viscera itself or it may be felt just deep in the skin that overlies the viscera. However, in many cases, pain cord segments may also be felt in a surface area of the skin far from the stimulated organ. This phenomenon is called refereed pain.

Pain originating from a particular viscus is usually felt at a distance from the site of the visceral organ involved. This may be because afferent fibers from the skin (dermatome) and viscera enter the same segment of the spinal cord.

The first-order neurons of the afferent fibers of both visceral and somatic are situated in the dorsal root ganglia of the spinal nerve.

Probably, both the fibers synapse with the common (same) second-order neuron of the dorsal grey horn of the spinal cord.

The axons of the second-order neuron reach higher centers (via the thalamus) which probably fail to recognize the source of pain (skin or viscera).

Automomic Nervous System Areas of referred pain on the body

Functions Of Autonomic Nervous System

  • Both sympathetic and parasympathetic systems of ANS innervate almost all the organs of the body. Thus, their action on one particular organ is antagonistic to each other.
  • If one system stimulates (excites) the organ, the other system depresses (inhibits) it. This is because their postganglionic neurons secrete different neurotransmitters
  • (Ach for parasympathetic and noradrenaline in case of sympathetic) and their effector receptors for parasympathetic and adrenergic receptors for sympathetic).
  • As the hypothalamus is the higher center of ANS it controls and balances the sympathetic and parasympathetic activities.
  • However, students should also note that organs such as sweat glands, arrector pili muscles, kidneys, adrenal medulla, and many blood vessels are innervated only by the sympathetic system of the autonomic nerves.
  • As there is no parasympathetic innervation in these organs, they do not face opposition. Thus, sympathetic stimulation leads to action while its inhibition leads to cessation of action.
  • For example, when sympathetic fibers release norepinephrine into the smooth muscles of blood vessels, blood pressure rises due to the contraction of smooth muscles by mediation of the al receptor.
  • Meanwhile, the epinephrine of circulating blood acts on the same smooth muscles by mediation of P2 receptors in the cell membrane leading to vasodilatation and a fall in blood pressure. Parasympathetic fibers do not terminate on many blood vessels.

Enteric Nervous System

The enteric nervous system (ENS) is defined as the system of neurons that is found within the wall of the GIT, gallbladder, and pancreas.

The entire length of GIT is supplied by sympathetic and parasympathetic parts of ANS.

The ANS forms the following two different nerve plexuses in the gut wall:

Submucosal plexus (plexus of Meissner): Situated in the subamucosa

Myenteric plexus (plexus of Auerbach): Situated in between circular and longitudinal muscle coats

Automomic Nervous System Referred pain from heart.

Automomic Nervous System Enteric Neurons, Myenteric And Meissners Plexus in the wall of the intestine

These plexuses consist of the following:

  • Parasympathetic preganglionic fibers terminate on postganglionic parasympathetic neurons situated in the myenteric plexus.
  • Postganglionic sympathetic and parasympathetic fibers forming a network in Meissner and myenteric plexuses
  • Sensory and motor enteric neurons and their processes consist of 100 million neurons in the plexuses of GIT.

All these innervate the mucosa, submucosa, muscle coats, and blood vessels. These regulate the secretion from the mucosal gland and motility of GIT.

The gallbladder and pancreas also have ganglia and nerve plexus. The ENS was previously considered a part of ANS.

However, now it is considered a system separate from the ANS. The neurons of the ENS arise from neural crest; thus, they differ from the origin of sympathetic and parasympathetic neurons.

Functions of the Enteric Nervous System

  • The functions of ENS include both sensory and motor.
  • The sensory neurons of ENS monitor the stretching of the walls of the intestine and chemical changes within the gastrointestinal tract.
  • The motor neurons of ENS control the contraction of the smooth muscle, secretion of the gastrointestinal gland, and endocrine cells associated with GIT.

Autonomic Nervous System Summary

  • The autonomic nervous system (ANS) innervates the cardiac muscle, smooth muscle (present in the wall of viscera and blood vessels), and glands.
  • The ANS works by forming the reflex arc which is organized in afferent (sensory) pathways, integrating higher centers and efferent (motor) pathways.
  • Visceral sensation hardly reaches the level of consciousness. The cell bodies of sensory neurons are situated in the sensory ganglia of cranial nerves and the dorsal root ganglia of spinal nerves.
  • The visceral activities are integrated at higher levels, especially in the hypothalamus.
  • Efferent pathways convey motor impulses from the CNS to the cardiac muscle, smooth muscles, and glands.

Two neurons are involved in this pathway:

  • Preganglionic and
  • Postganglionic neurons.

The visceral motor signals reach various organs through two major subdivisions of the ANS:

  • Sympathetic and
  • Parasympathetic nervous systems.

Sympathetic nervous system

  • The preganglionic motor neurons are situated in the lateral horn of the grey matter of the spinal cord from T1 to L2 segments.
  • The postganglionic motor neurons of this division are situated in the sympathetic trunk ganglia and prevertebral ganglia.
  • The preganglionic fibers reach the sympathetic trunk ganglion through white rami communicans while the postganglionic fibers after coming out through the sympathetic ganglia join the ventral ramus through grey rami communicans.
  • Some preganglionic sympathetic fibers, which do not relay in the sympathetic chain (paravertebral), may relay in the prevertebral ganglion through splanchnic nerves.

Parasympathetic nervous system

  • The parasympathetic nervous system consists of cranial and ‘sacral’ outflow.
  • The preganglionic parasympathetic fibers of both cranial and sacral outflow end in ‘terminal ganglia’ containing postganglionic parasympathetic neurons.
  • The terminal ganglia associated with cranial outflow are the ciliary, pterygopalatine, submandibular, and otic ganglia. The terminal ganglia of the vagus and sacral outflow are situated in the wall of the viscera and are unnamed.
  • The actions of sympathetic and parasympathetic parts of ANS on any particular organ are antagonistic to each other.

Enteric nervous system

  • The enteric nervous system (ENS) consists of motor, sensory, and interneurons, which are found within the walls of GIT.
  • The functions of ENS include both sensory and motor.

Autonomic Nervous System Multiple Choice Questions

Question 1. The following structures are innervated by ANS except

  1. Smooth muscles of viscera
  2. Smooth muscles of blood vessels
  3. Cardiac muscles
  4. Glands
  5. Articular capsule of joints

Answer: 5. Articular capsule of joints

Question 2. Which of the following facts about visceral sensations are true?

  1. They hardly reach the level of consciousness
  2. Sensations of nausea and retrosternal pain are perceived
  3. The sensation of distension of the bladder and bowel reaches the level of consciousness
  4. Pain sensation from the viscera is perceived as secondary to a lack of oxygen supply
  5. All of the above

Answer: 3. Sensation of distension of bladder and bowel reach the level of consciousness

Question 3. Which of the following facts about the autonomic motor pathway is false?

  1. Visceral motor signals reach organs through the sympathetic and parasympathetic nervous systems
  2. Both sympathetic and parasympathetic pathways consist of two neurons—preganglionic and postganglionic
  3. Preganglionic neurons are situated in the CNS while postganglionic in the peripheral ganglion
  4. The axons of preganglionic neurons are myelinated and synapse with postganglionic neurons
  5. None of the above

Answer: 5. None of the above

Question 4. Which ofthe following statements about the sympathetic nervous system is false?

  1. Preganglionic sympathetic neurons are located in the lateral horn of the spinal cord from T1 to L2 and from S2 to S4 spinal segments
  2. Postganglionic sympathetic neurons are located in the sympathetic trunk (sympathetic chain) ganglia
  3. They are also located in prevertebral ganglia
  4. Prevertebral sympathetic ganglia are situated in front of the vertebral column

Answer: 1. Preganglionic sympathetic neurons are located in the lateral horn of the spinal cord from T1 to L2 and from S2 to S4 spinal segments

Question 5. Prevertebral sympathetic ganglia consist of the following except

  1. Pulmonary ganglion
  2. Superior mesenteric ganglio
  3. Inferior mesenteric ganglion
  4. Celiac ganglion

Answer: 1. Pulmonary ganglion

Question 6. Which of the following statements about splanchnic nerves is false?

  1. They arise from the thoracic sympathetic chain
  2. They are medically directed branches of the sympathetic trunk
  3. They contain postganglionic myelinated nerve fibers
  4. There are three splanchnic nerves—greater, lesser, and least splanchnic nerves
  5. These splanchnic nerves reach the prevertebral ganglion

Answer: 3. There are three splanchnic nerves—greater, lesser, and least splanchnic nerves

Question 7. The following facts about the distribution of sympathetic fibres are true except

  1. Preganglionic sympathetic fibers travel in the ventral spinal nerve root
  2. They then travel in the ventral ramus of spinal nerves
  3. They soon leave the ventral ramus to join the sympathetic trunk through the white ramus communicans to synapse with the postganglionic neurons
  4. The axons of postganglionic neurons join the ventral ramus again through grey ramus communicans
  5. Grey ramus communicans contain myelinated fibers of postganglionic neurons

Answer: 5. Grey ramus communicans contain myelinated fibers of postganglionic neurons

Question 8. Following is the location of preganglionic motor neurons of the parasympathetic nervous system except

  1. Few cranial nerve nuclei in the brainstem
  2. Lateral horn of spinal cord between S2 and S4 spinal segments
  3. Terminal ganglia of the parasympathetic nervous system
  4. Pterygopalatine ganglion

Answer: 3. Terminal ganglia of the parasympathetic nervous system

Question 9. Which of the following statements is false?

  1. Acetylcholine (ACh) is liberated at the terminals of preganglionic parasympathetic neurons
  2. ACh is liberated at the terminals of preganglionic sympathetic neurons
  3. Adrenaline is liberated at the terminal of postganglionic parasympathetic neurons
  4. ACh/norepinephrine is liberated at the terminals of
    postganglionic sympathetic neurons

Answer: 3. Adrenaline is liberated at the terminal of postganglionic parasympathetic neurons Part of the thalamus, subthalamus, middle and posterior parts of the hypothalamus, part of the midbrain