Skeletal system

SKELETAL SYSTEM
Presented by
Ms.P.Pavithra.,M.Pharm
Assistant Professor,
Dept. of Pharmacology,
SVCP

Skeletal system
The skeletal system is the structural framework that supports a body.
It also provides protection for a soft tissues and internal organs and serves as an
attachment for the body's muscles that push against it and apply force, resulting in
movement.
Study of structure and function of Skeletal system-Osteology
Skeletal system consists of
• Bones
• Joints
• Cartilages
• Ligaments

Functions of Skeletal system
 SUPPORT: Hard framework that supports and anchors the soft organs of the body.
 PROTECTION: Surrounds organs such as the brain and spinal cord.
 MOVEMENT: Allows for muscle attachment therefore the bones are used as levers.
 STORAGE: Minerals and lipids are stored within bone material.
 BLOOD CELL FORMATION: The bone marrow is responsible for blood cell
production.

Bone
Hard, dense, calcified tissue that forms the skeleton of most
vertebrates.
It serves as a framework for the attachment of muscles and protects
vital organs such as Brain.

Classification of Bones
1. Long bones
2. Short bones
3. Flat bones
4. Irregular bones
5. Sesamoid bones

1.) Long bones:
They found in the limbs. A long bone contains a shaft and contains two
extremities. The long bones acts as a lever and help in various movements of the body.
Example:
 Humerus
 Femur

2.) Short bones:
These have no shaft. But they contain a spongy substance covered by a shell of
compact bone.
Example:
 Small bones of wrist and ankle

3.) Flat bones:
They contain two layers of compact bone with a spongy substance in between.
Its main function is to protect vital organs and being a base for muscular attachment.
Example:
 Pelvic bones
 Scapula
 Sternum (breast bone)
Scapula

4.)Irregular bones:
These are bones in the body which do not fall into any other category, due to their
non-uniform shape. They primarily consist of cancellous bone, with a thin outer layer of
compact bone.
Example:
 Vertebrae
 Bones of the face Irregular bones

5.) Sesamoid bones:
These are small bones which develop in the tendons of muscles.
Example:
 Patella of knee joint

Structure of Bones
 Bone is the hardest of the connective tissues.
 It consists of two kinds of connective tissue
1.) Compact bone: It is hard and dense. It is found in flat bones, in the shafts of long
bones and as a thin covering of all bones.
2.) Cancellous/Spongy bone: It is spongy in appearance. It is found in the ends of long
bones, in short bones and in between two layers of compact tissue of flat bones.

Structure of Bones……
GROSS STRUCTURE OF A LONG BONE:
 A long bone has two ends (epiphysis) connected by
a shaft (diaphysis).
 The outer membrane covering the bone is
periosteum.
 Endosteum is the inner surface of bony tissue.
 Medullary cavity is the central cavity of bone
shafts where red bone marrow and yellow bone
marrow is stored. Hence, the medullary cavity is
also known as Marrow cavity.
 Nutrient foramen is the opening through which
arteries pierce the medullary canal.

Structure of Bones……
MICROSCOPIC STRUCTURE OF BONE:
Cross section of a bone under the microscope shows the following structures:
 Haversian canal which lies at the centre. It contains blood vessels, nerves and
lymphatics.
 Lamellae which are plates of bone arranged concentrically around the haversian
canal.
 Lacunae which are spaces between the lamellae and they contain bone cells.
 Canaliculi which are fine channels. They radiate between the lacunae and the central
haversian canal.
All the structures together form a unit. This unit is called as the Haversian system.

Types of Bone Cells
1.) Osteocytes------Mature bone cells
2.) Osteoblasts------Bone-forming cells
3.) Osteoclasts------Bone-destroying cells

Development & Growth of Bone
 In embryos, the skeleton is primarily hyaline cartilage
 During development, much of this cartilage is replaced by bone
Cartilage remains in isolated areas
Bridge of the nose
Parts of ribs
Joints

 Formation of the bone is called as Ossification.
Bones of the skeleton are developed in two ways:
 Some bones develop in sheets of fibrous tissue (intra-membraneous
ossification).
 Other bones develop in bars of cartilage (intra-cartilaginous ossification).
In both cases, bone cells called Osteoblasts invade the area of ossification.
 Here, calcium salts are deposited to give the necessary hardness. Thereby
process of bone development occurs.
After birth, the bone grows from certain centres in it.

 The centre in the shaft is called diaphysis.
 The two centres in the ends are called as epiphysis.
 The layer of cartilage in between the epiphysis and diaphysis is called as
epiphyseal cartilage.
 This is gradually replaced by bone.
 This replacement occurs till the epiphysis and diaphysis unite to form a
single bony structures.
 After this, growth of bone stops.

Divisions of Human skeleton
The skeleton is subdivided into two major divisions
I.) Axial skeleton
II.) Appendicular skeleton

Axial skeleton
Appendicular skeleton

I.) Axial skeleton
The axial skeleton consists of :
A. Skull
B. Hyoid bone
C. Auditory ossicles
D. Vertebral column (spinal column)
E. Thoracic cage
F. Sternum

A.) Skull
The skull is situated on the upper end of vertebral column and its
bony structure is divided into 2 parts,
 Cranium(Brain box)
 Facial bones
Axial skeleton……

CRANIUM
Skull……
Cranium is formed by 8 bones
They are
1.) Frontal bone---1
2.) Parietal bone---2
3.) Temporal bone---2
4.) Occipital bone---1
5.) Sphenoid bone---1
6.) Ethmoid bone---1

Cranium……
Sutures of the Cranium:
• Sutures are the immovable joints which unite the bones of the skull.
• The important sutures are:
 Coronal sutures: between the frontal bone and the two parietal bone.
 Sagittal suture: between the two parietal bones.
 Lambdoid suture: between the occipital bone and the two parietal bones.
Occipital bone
Parietal bone
Frontal bone

Cranium……
Cranial fossae:
• The base of the skull is divided into three fossae.
• They are:
 Anterior cranial fossa: It is formed by horizontal plates of frontal bone.
 Middle cranial fossa: Formed by sphenoid bone and petrous portion of
temporal bones.
 Posterior cranial fossa: Formed mainly by the occipital bone.

Cranium……
It forms the forehead and the roof of the orbit. The features of frontal
bone are:
 Supraorbital margins-----form the arches of orbit.
 Nasal notch------bone projecting between supraorbital margins. Nasal bones are
fitted to this.
 Superciliary arch----lies above these two structures
 Frontal tuberosities-------prominences of forehead---Frontal squama &
eminence
 Frontal sinus-----a space behind the forehead. It contains air and is lined by
mucous membrane.
1.) Frontal bone

Cranium……
They are two in number. Both form the roof and sides of the skull. It has four
borders, four angles and two surfaces.
i.) The articulation of this bone are:
 Anteriorly with frontal bone
 Posteriorly with occipital bone
 Medially with other parietal bone
 Below with the temporal bone
2.) Parietal bone

Cranium……
ii.) It contains an eminence called parietal tuberosity.
iii.) Superior and inferior temporal lines are the two lines which run
parallel to each other.
iv.) The inferior surface is concave. It has impressions for meningeal
vessels.
2.) Parietal bone

Cranium……
They are two in number. They form lower part of the sides of the skull.
The parts of temporal bone are:
i.) Squamous part-----a flat part having the zygomatic process which is connected
to zygomatic bone.
ii.) Petrous part----forms the bone of internal ear.
iii.) Mastoid part----contains mastoid process.
iv.) Tympanic part----contains the external auditory meatus.
3.) Temporal bone

Cranium……
3.) Temporal bone

Cranium……
It is at the back and lower part of the cranial cavity. The features of
occipital bone are:
i.) A prominence above called as external occipital protruberance.
ii.) Condyles, two in number which articulate with atlas.
iii.) An opening at the base of skull called foramen magnum. The spinal cord
passes through this opening.
4.) Occipital bone

Cranium……
It lies at the base of the skull. It forms a large part of middle cranial fossa.
It contains:
i.) Two pairs of wing-like structures called greater and lesser wings.
ii.) Sella turcica or hypophyseal fossa which is a fossa for the pituitary gland.
5.) Sphenoid bone

Cranium……
It is cubical in shape. It is very light and thin. It is situated at the roof of
nose and in between the orbits. It contains:
i.) Two labyrinths composed of ethmoidal sinuses.
ii.) A perpendicular plate forming the upper part of nasal septum.
iii.) Cribriform plate fitting into a notch of frontal bone. Olfactory nerves pass
through perforations in this plate.
6.) Ethmoid bone

Cranium……
Fontanelles:
• At birth, skull bones of the child are not completely ossified. The space between the
bones are filled by membranes. These membranes at the angles of bones are called
fontanelles. These fontanelles are:
 Anterior fontanelles: It is the largest of the fontanelles. It is diamond
shaped. It is situated at the junction of frontal and two parietal bones. Here,
the coronal and sagittal sutures meet. This fontanelle closes at the age of 1
year and 6 months.
 Posterior fontanelle: It is at the back. It occurs at the junction of two
parietal and the occipital bones. It closes soon after birth.

Cranium……
Sinus of the Skull:
These are cavities or chambers present in the bones of the skull. The important
sinuses are:
i.) Frontal sinus: They are two in number present in the frontal bones. They are present
on each side at the roof of the nose.
ii.) Maxillary sinuses: Two in number present in the maxillary bones. They lie on each
side of the nose.
iii.) Ethmoidal and sphenoidal sinuses: They are the other sinuses present in the skull.
All these sinuses communicate with the nose.

The bones which make the face are 14 in number.
These bones are:
1.) Maxillae(upper jaw)----2
2.) Mandible(lower jaw)-----1
3.) Palate bones----2
4.) Zygomatic bone----2
5.) Lacrimal bones----2
6.) Nasal bones----2
7.) Inferior Turbinate bones-----2
8.) Vomer-----1
FACIAL BONES
Skull……

Facial bones……
They are two in number. These bones form the upper jaw. The essential
features of maxillae are:
i.) A body which is pyramidal in shape.
ii.) Four processes namely zygomatic process, alveolar process, frontal process and
palantine process.
iii.) Maxillary sinus present in the internal aspect.
1.) Maxillae

Facial bones……
This bone forms the lower jaw and is the only movable bone of skull.
It contains:
i.) A body which is the horizontal part in the centre. It contains the lower teeth and
forms the chin.
ii.) Two rami, one on each side. Each ramus contains the coronoid process in the front
and condyle of jaw(head) which lies behind.
Tempero-mandibular joint is formed by the articular of condyle with the
temporal bone.
2.) Mandible

Facial bones……
3.) Palate bones: They are two in number. They form the roof of the mouth cavity
and the hard palate.
4.) Zygomatic /Cheek bones: They are two in number. They form a part of the
floor of the orbit. Each of them contains a temporal process. This process joints with
the zygomatic process of temporal bone and forms the zygomatic arch.
5.) Lacrimal bones: They are two bones found in the interior of the orbit. It
contains the lacrimal sac which secretes the lacrimal fluid.

Facial bones……
6.) Nasal bones: They are two in number. They form the nasal bridge.
7.) Inferior turbinate bones: They are two in number. They are also called as
nasal conchae. They found in the interior of the nasal cavity.
8.) Vomer: It forms the lower part of nasal septum.

B.) Hyoid bones:
It is V shaped bone.
It has---a body and two horns (lesser and greater horn).
The hyoid bone holds up the tongue, which sits above it, and
holds up the larynx, which hangs below it.
Hyoid bone----Free floating bone.

C.) Auditory ossicles
Auditory ossicles is also known as Sensory capsule/Ear ossicle.
It consist of 6 bones, 3 in each ear.
1.) Malleus(1)------Hammer shaped
2.) Incus(1)-------Anvil shaped
3.) Stapes(1)------Stirrup shaped

D.) Vertebral column (spinal column)
The vertebral column(spinal column) is made of a number of
bones. These bones are called vertebrae.
33 vertebrae

Classification of Vertebrae
According to the region they occupy, the vertebrae are classified as
1.) Cervical vertebrae(7): They form the neck region.
2.) Thoracic vertebrae(12): They form back of thorax.
3.) Lumbar vertebrae(5): They form lumbar region.
4.) Sacral vertebrae(5): They form the sacrum.
5.) Coccygeal vertebrae(4): They form coccyx.

Vertebral column……
Except the first and second cervical vertebrae (atlas and axis), other
vertebrae have similar characteristics.
So these other vertebrae are called as typical vertebrae.

Structure of a typical vertebrae
A typical vertebrae contains
1.) A body which is a box shaped anterior part. It is slightly concave in the upper and
lower surface.
2.) Neural arch which is the posterior part. It contains a.) two pedicles which project
backward and b.) two laminae which are directed backward to meet behind in the mid-
line.
3.) Two transverse processes, one on each side. They lie in the junction between
pedicle and lamina.

Structure of a typical vertebrae
4.) One spinous process which is a backward projection. It occurs where the two
laminate unite in the mid-line.
5.) Two articular processes, in the upper and lower surface. They lie at the junction
between pedicle and laminae(near the transverse process).
6.) Neural canal/Vertebral foramen which is a circular opening. The spinal cord
passes through this.

1.) Cervical vertebrae
 They are seven in number.
 The first cervical vertebra is called as Atlas.
 The second cervical vertebra is called as Axis.
These two cervical vertebrae have different structures when compared with others.
ATLAS:
It is the first cervical vertebrae.
It does not have a body.
On the upper surface, it has two facets.
These facets articulate with the condyles of occipital bone( to form atlanto-occipital
joint.)
Atlas

AXIS:
 It is the second cervical vertebrae.
 It contains
1.) Odontoid process which is an upward projection from the body. It articulates with
anterior arch of atlas.
2.) Two facets on the anterior surface. They articulate with atlas.
3.) A spine which is small and bifid.
Other cervical vertebrae:
They are the lower five. Their features are 1.) a smaller body 2.) oblong shape
3.) triangular neural canal 4.) bifid spinous process 5.) vertebral foramen in the transverse
process.
Vertebral column…… Axis

2.) Thoracic vertebrae
 They are twelve in number. These vertebrae carry the ribs. The characteristic features
of these vertebrae are:
 Body is heart shaped.
 Body has facets, one on each side for the attachment of head of ribs.
 The transverse process has facets at the tips for articulation with tubercle of ribs.
 Vertebral foramen is present.
 Pedicle and laminae are present.
 Spinous process is long and projects downwards.

2.) Thoracic vertebrae

3.) Lumbar vertebrae
 They are five in number. They have the following characteristics:
 Body is big and kidney shaped.
 Spinous process is short, stout and directed back-wards.
 No articular facets for ribs.
 Pedicles and laminae are present.

4.) Sacral vertebrae
 They are five in number. All of them unite to form a single bone called sacrum. The sacrum
joints with the pelvic bone and takes part in the formation of pelvic cavity. The features of
sacrum are:
 Sacral foraminae which are four openings present in the anterior surface. Nerves pass through
these openings.
 Lateral masses on either side. They are formed by the union of transverse processes.
 Sacral promontary which is the projection of the upper part of sacrum.

5.) Coccygeal vertebrae
 They are four in number.
 All of them unite to form a single bone called coccyx.

Curves of the vertebral column
 When viewed from the side the vertebral column
presents four curves, two primary and two secondary.
 The fetus in the uterus lies curled up so that the head
and the knees are more or less touching. This position
shows the primary curvature.
 The secondary cervical curve develops when the
child can hold up his head (after about 3 months) and
the secondary lumbar curve develops when he stands
upright (after 12 to 15 months). The thoracic and
sacral primary curves are retained.

Functions of the vertebral column
 The vertebral foramina form the vertebral canal which provides a strong bony
protection for the delicate spinal cord lying within it.
 The pedicles of adjacent vertebrae form intervertebral foramina, one on each side,
providing access to the spinal cord for spinal nerves, blood vessels and lymph
vessels.
 The numerous individual bones enable a certain amount of movement.
 It supports the skull.
 The intervertebral discs act as shock absorbers, protecting the brain.
 It forms the axis of the trunk, giving attachment to the ribs, shoulder girdle and upper
limbs, the pelvic girdle and lower limbs.

E.) Thoracic cage
• RIBS- They are arranged in 12 pairs, on the back side, all of them are attached
to thoracic vertebrae.
Costal cartilages-----contribute to the elasticity of the thoracic cage
Depending on their attachment in the front, they are classified as:
a. True ribs- They are upper seven pairs. They are attached to the sternum directly.
b. False ribs-They are lower five pairs, and are attached to the sternum
indirectly(through costal cartilages).
c. Floating ribs- They are the lowest two pairs. They are not attached in front.

Functions of Thoracic cage
Enclose and protect the organs in the thoracic and abdominal cavities
Provide support for the bones of the upper limbs
Play a role in breathing

F.) Sternum
• It is also called Breast bone. It is 15 cm long. It is located in the center of
the thoracic wall.
• It is a flat bone which is divided into three parts namely
i. Manubrium sterni
ii. Body of sternum(Gladiolus)
iii. Xiphoid bone(Ensiform process)

Sternum……
i.) Manubrium sterni:
It is the upper part which is triangular in shape. It contains
Clavicular notches on both sides. These notches articulate with clavicle.
Suprasternal/Jugular notch which is present in between the two clavicular
notches.
Articular surfaces on both sides for the first ribs.

ii.) Body of Sternum(Gladiolus):
The second rib is attached at the junction between manubrium sterni and
body of sternum.
This junction is called as Angle of Ludwig/Sternal angle.
The body of sternum has attachments for 3rd, 4th, 5th, 6th and 7th ribs.
Sternum……

iii.) Xiphoid bone(Esniform process):
It is the lowest part of sternum.
To this are attached the diaphragm, linea alba and rectus abdominis muscle.
Sternum……

Appendicular skeleton
The appendicular skeleton consists of :
A.) Bones of Pectoral girdle
B.) Bones of Upper limbs
C.) Bones of Lower limbs
D.) Bones of Pelvic girdle

A.) Bones of Pectoral girdle/Shoulder girdle
Bones of pectoral girdle includes
1.) Scapula
2.) Clavicle

Bones of Pectoral girdle……
Scapula are 2 in number.
It lies at the back of the thorax.
It forms the posterior part of the shoulder girdle.
It has two surfaces, three angles and three borders.
1.) Scapula

The surfaces of scapula are:
i.) Anterior or costal surface: It is called as the suprascapular fossa. It
lies nearest to the ribs. Subscapular muscle is attached to this surface.
ii.) Posterior or dorsal surface: It is divided into two fossae by spine of
scapula which ends with acromian process.
1.) Scapula
Posterior surface

The fossae are:
a.) Supraspinous fossa which is the upper one. It gives attachment to
supraspinous muscle.
ii.) Infraspinous fossa which is below. It gives attachment to infraspinous
muscle.
1.) Scapula

The borders of scapula are:
i.) Superior border: It lies in the upper part. It extends from the superior angle to the
base of coracoid process. Suprascapular notch is the inner extremity of this border. The
suprascapular vessels pass through this notch.
ii.) Medial or vertebral border: It is nearest to vertebral column. It extends between
superior and inferior angles.
iii.) Lateral or axillary border: It is nearest to axilla. It lies between inferior angle and
glenoid cavity.
1.) Scapula

The angles of scapula are:
i.) Superior angle: It lies at the junction between superior and medial borders.
ii.) Inferior angle: It is the junction between medial and lateral borders. It is the lowest
point of the scapula.
iii.) Lateral or external angle: It contains glenoid cavity which receives the head of
humerus (to form shoulder joint). Coracoid process of scapula arises internal to glenoid
cavity.
1.) Scapula

Clavicle are 2 in number.
It is also called as collar bone.
It is a long and curved bone.
It forms the anterior part of shoulder girdle.
It contains a shaft, two ends and four borders.
The ends are:
1.) Medial or sternal end: It articulates with sternum.
2.) Lateral or acromial end: It articulates with acromion process of scapula.
The borders of clavicle are superior, inferior, anterior and posterior borders.
2.) Clavicle

B.) Bones of Upper limbs
Bones of Upper limbs includes
1.) Humerus
2.) Ulna
3.) Radius
4.) Carpals
5.) Metacarpals
6.) Phalanges

1.) Humerus
 Humerus are 2 in number.
 It is the longest bone of upper limb.
 It contains two extremities and a shaft.
Upper extremity: It contains
A hemispherical head which articulates with glenoid
cavity of scapula ( at the shoulder joint)
Anatomical neck which is below the head.
Greater tuberosity which is below the anatomical
neck. It is in the outer side of upper extremity.
Lesser tuberosity which is also below the anatomical
neck. But it is at the front.
Bones of Upper limbs……

1.) Humerus
 Bicipital groove or intertubercular sulcus: It lies in
between these two tuberosities.
 Surgical neck: It is a narrow point of the bone below the
two tuberosities.
Shaft:
It contains
 Deltoid tuberosity which is a rough tubercle on the
lateral aspect of the shaft. It receives the insertion of
deltoid muscle.
 Spiral or radial groove which is a oblique groove across
the back of the shaft. The radial nerve passes through this
groove.

1.) Humerus
Lower extremity: It contains
 Trochlea which is a pulley-shaped surface on the innerside.
It articulates with ulna.
 Capitulum on the other side. It articulates with radius.
 Coronoid fossa which is a depression. It lies above the
articulating surface for ulna.
 Olecranon fossa which lies at the back. It receives the
olecranon process of ulna.
 Medial and lateral epicondyles which lie on each side of
the articulating surfaces.

2.) Ulna
 Ulna are 2 in number.
 It is the inner most bone of the fore arm.
 It contains two extremities and a shaft.
Coronoid process which is a projection in front.
It fits into the coronoid fossa of humerus.
Olecranon process which is an upward
projection at the back. It fits into olecranon fossa
of humerus.
Trochlear notch which is formed by these two
processes. It articulates with trochlear surface of
humerus.

2.) Ulna
Radial notch which is on the outer or lateral
aspect. It articulates with head of radius.
Shaft:
It is tapering towards the lower end. It contains
surfaces and borders.
It gives attachment to
 Muscles which control movements of wrist and
fingers.
 Flexor and extensor muscles of forearm.
 Muscles of pronation and supination of forearm.

2.) Ulna
Head of ulna which is a small rounded
eminence. It articulates with lower extremity of
radius.Styloid process which projects
downwards from back of lower extremity.

3.) Radius
 Radius are 2 in number.
 It is the lateral or outer most bone of forearm. It
contains two extremities and a shaft.
A head which is more or less button-shaped.
Neck which lies below the head.
Biceps tubercle (radial tuberosity)which lies
below and to the medial side of neck. It gives
insertion to biceps muscle.

3.) Radius
Shaft:
 It is narrower above and wider below.
It contains surfaces which give attachment to a
variety of muscles.
Lower extremity: It contains styloid process
which is on the outer or lateral aspect.

4.) Carpals
Carpals----16
Bones of wrist------------Carpals---- are arranged in two rows.
 They are:
First or proximal row made of scaphoid, lunate, triquetrum and pisiform bones.
Second or distal row made of trapezium, trapezoid, capitate and hamate bones.

5.) Metacarpals
Metacarpals--10
Bones of Palm------Metacarpals.
They are long bones which contain a head, a shaft and a base.
The bases articulate with the distal row of carpal bones. The heads
articulate with the proximal row of phalanges.

6.) Phalanges
Phalanges-28
Bones of fingers--------Phalanges
These are long bones.
The thumb has two phalanges. Other fingers have three phalanges.
They are proximal, middle and distal phalanges.

C.) Bones of Lower limbs
Bones of lower limbs includes
1.) Femur
2.) Patella
3.) Tibia
4.) Fibula
5.) Tarsals
6.) Metatarsals
7.) Phalanges

1.) FEMUR
Femur----2 in number.
It is also called as thigh bone.
It is the longest and strongest bone of the skeleton.
It contains two extremities and a shaft.
Bones of lower limbs……

1.) FEMUR
i.) A head which is spherical and covered with
hyaline cartilage.
ii.) A neck which lies below the head. It is long and
flattened.
iii.) Greater trochanter which is on the outer side
where the neck joins the shaft.
iv.) Lesser trochanter which is on the inner side
where the neck joins the shaft.
v.) Anterior and posterior inter-trochanteric lines are
two lines which unite greater and lesser trochanters.
Anterior view Posterior view

1.) FEMUR
Shaft:
It is smooth, cylindrical and rounded in front and at
the sides.
It contains
i.) Linea aspera which is a ridge on the posterior
aspect.
ii.) Gluteal ridge which extends from linea aspera to
the back of greater trochanter.
iii.) Pectineal/Spiral line which extends at the inner
aspect from linea aspera to lesser trachanter.

1.) FEMUR
i.) Medial and lateral condyles lying one on each
side.
ii.) Intercondylar notch which lies behind.
It separates these two condyles.
iii.) Adductor tubercle which is a small tubercle
above the medial condyle.
iv.) Patellar surface which separates the two
condyles in front. Patella rests on this surface.
v.) Popliteal surface which is above the condyles
at the back. Popliteal vessels and nerves lie on this
surface.

2.) PATELLA
Patella---2 in number.
It is a sesamoid bone developed in the tendon of quadriceps femoris muscle.
It contains
i.) An apex pointing downwards. The ligamentum patellae is attached to the
apex.
ii.) An anterior surface which is rough and covered with a bursa.
iii.) Posterior surface which is smooth. It articulates with patellar surface of
femur (to form knee joint).

3.) TIBIA
 Tibia----2 in number.
 It is the innermost bone of the leg.
 It is a long bone containing two extremities
and a shaft.
i.) A head which contains two condyles namely
medial condyle and lateral condyle. The upper
surfaces of these condyles articulate with the
corresponding condyles of femur.
ii.) Popliteal notch which separates the two
condyles at the back.
iii.) Tubercle of tibia(Tibial tuberosity) which
lies below the condyles in the front.

3.) TIBIA
Shaft:
It is triangular in shape having three borders and three
surfaces. The shaft contains
i.) Crest of tibia which is present in the middle third of the
anterior border.
ii.) Soleal line which is a strong ridge of bone present in the
posterior surface.
Lower extremity:
 It is slightly expanded. It has an articular surface for talus
to form the ankle joint.
 Medial malleolus is a downward projection present in the
medial aspect.

4.) FIBULA
 Fibula----2 in number.
 It is the lateral or outermost bone of the leg.
 It is a long and slender bone.
It contains two extremities and a shaft.
i.) A head which is expanded. It articulates with the back of
lateral condyle of tibia. It does not take part in the formation
of knee joint.
ii.) Styloid process present in the apex of head. One
ligament of knee joint is attached to this.

4.) FIBULA
Shaft:
It is thin and gives attachment to several
muscles.
Lower extremity:
It contains
i.) Lateral malleolus which is a downward
prolongation of the lower extremity.
ii.) Malleolar fossa which is a rough depression
behind the malleolus.

5.) TARSALS
Bones of Ankle----TARSALS(14)
They include calcaneum, talus, navicular, cuboid and three cuneiform bones.
 CALCANEUM: It is the largest bone of the foot. It lies at the back of foot.
Above, it articulates with talus and in front with cuboid.
 TALUS: It forms the central and highest point of foot. It articulates at the sites
with medial and lateral malleoli and below with calcaneum.
 NAVICULAR(SCAPHOID): It is a disc shaped bone. It is present in the
medial aspect of foot. It lies between talus at the back and three cuneiform bones
in front.

5.) TARSALS
 CUBOID: It is in the lateral aspect of foot. Behind, it articulates with calcaneum.
In front, it articulates with two lateral metatarsal bones.
 CUNEIFORM BONES: They are three in number namely medial, intermediate
and lateral cuneiform bones. Posteriorly they articulate with navicular bone.
Anteriorly they articulate three metatarsal bones.

6.) METATARSALS
Bones of Sole-----Metatarsals(10)
 They are five in number. They correspond with the five toes. All of them are long
bones.
 They contain a head, shaft and base.
 The first metatarsal is thick and stout.
 The second metatarsal is longer than others.
 The fifth one has a projection at the lateral side of the base.

7.) PHALANGES
Bones of Toes----Phalanges(28)
They are 14 bones (in each leg), two for the first toe and three for the rest. All of
them are long bones.
Phalanges------Proximal, Middle and Distal phalanges.

D.) Bones of Pelvic girdle
The pelvic girdle is the connection between the trunk and lower limbs. It is
formed by 4 bones
Bones of pelvic girdle includes
1.) Two Innominate bones, one on each side
2.) Sacrum
3.) Coccyx

Bones of Pelvic girdle……
 It is called as pelvic bone or hip bone. It is made of three parts namely ilium,
ischium and pubis.
 All these three bones unite to form a large cup shaped cavity on the outer surface
called acetabulum. The head of femur fits into acetabulum forming the hip
joint.
1.) INNOMINATE BONE:

ILIUM: It is the upper expanded and flat part of innominate bone. It contains:
i.) External or gluteal surface: This surface contains three ridges namely superior,
middle and inferior gluteal ridges. They give attachment to gluteal muscles.
ii.) Internal surface which is concave. It forms part of iliac fossa and it gives
attachment to iliac muscles.

iii.) An upper margin called as crest of ilium. The crest of ilium contains four
spines. They are
a.) Anterior superior iliac spine
b.) Posterior superior iliac spine
c.) Anterior inferior iliac spine
d.) Posterior inferior iliac spine
iv.) Great sciatic notch which is below the articulating surface for sacrum.

PUBIS:
It is the front portion of innominate bone.
It contains
i.) A body which is more or less square in shape.
ii.) Symphysis pubis which is the union of the pubic bones in the front.
iii.) Superior ramus which is a bridge of bone projecting from the outer
part of body and joins it to ilium.
iv.) Inferior ramus which is the lower part of the body and joins it to
ischium.

ISCHIUM:
It is the solid, broad portion at the lower and back part of innominate bone. It
contains
i.) A body which forms acetabulum on the outer surface.
ii.) Tuberosity of ischium present at the lowest point. It supports the body weight
while sitting.
iii.) Spine of ischium which arises from the back of ischium.
Obturator foramen is a roughly triangular opening which is bounded by :
• Pubic bone
• Ischium behind and below

Parts of pelvis :
Pelvis can be divided into
1.) False pelvis which is the upper part. It is formed by the two iliac bones.
2.) True pelvis which is the lowest part. It is formed by ischium and pubis (in the
front and on each side) and by sacrum(behind).
• Pelvic brim is the upper opening of true pelvis.
• Iliopectineal line is the line present at the junction of ilium with ischium.

Differences between female and Male pelvis
The female pelvis is adapted for pregnancy and child birth. It differs from male pelvis
in the following aspects:
• It is shallow and wider than male pelvis.
• Inlet and outlet are longer and nearly oval in shape.
• Bones are lighter and smoother.
• Pubic arch is wider.
• Ischial tuberosities are further apart.
• The coccyx is more movable.

Skeletal system

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