It consists of axial skeleton and appendicular skeleton. Axial skeleton includes skull or cranium, facial bones, hyoid bone, vertebral column and ribs. Appendicular skeleton includes pectoral girdle, pelvic girdle, forelimbs and hindlimbs.
|Human skull (side view)|
The skull or cranium is a box cavity containing and protecting brain. The bones of the skull are mostly flat and come close together at joints called sutures, they are immovable. The cranium consists of eight bones out of which four are unpaired and two are paired. The bones of the cranium are: (a) Frontal bone (b) Parietal bones (left and right) (c) Occipital bone (d) Temporal bone (left and right) (e) Ethmoid bone (f) Sphenoid bone.
These are 14 in number out of which 6 are paired and 2 are unpaired, and are attached to the cranium. They support the muscles of the face, mouth and nose. The paired bones of face are:
(b) Zygomatic bones
(c) Nasal bones
(d) Inferior nasal concha
(e) Lacrimal bones
(f) Palatine bones are two irregular bones, which form the back of the hard palate.
The unpaired bones are
(ii) Vomer (is only movable)
|Inferior nasal concha|
|An inferior view of the skull|
|Interior view of Hyoid Bone|
It is a small bone which lies at the tongue. It gives attachment to the tongue and serves as the site for the attachment of muscles associated with swallowing. It does not articulate with any other bone of head. It has a body, two greater and two lesser cornu. It is attached to the temporal bone muscles and ligaments.
It supports the weight of the body. It provides axial support to the head. Normally the vertebral column has four curvatures that provide more resiliency and strength in an upright posture than a straight column could. The vertebral column in human being consists of 33 vertebrae. The vertebrae are named according to their location in the vertebral column and may be divided into following groups:
a) Cervical vertebrae - (07)
b) Thoracic vertebrae - (12)
c) Lumbar vertebrae - (05)
d) Sacral vertebrae - (05)
e) Coccygeal vertebrae - (04)
Cervical vertebrae are the vertebrae of neck. There are seven such vertebrae in necks of all mammals. The first two vertebrae are modified to allow the movements of the head.
Atlas: The atlas is the first cervical (neck) vertebral
Axis: it’s the second cervical vertebra.
Thoracic vertebrae: These are the rib carrying vertebrae and form a backward curve down the thorax. These are characterized by their large spinous processes. The ribs articulate with the rib facet.
Lumbar vertebrae: These are strong stout bones with no rib articulations. These are the largest bones in the vertebral column.
Sacral vertebrae: These are five fused vertebrae forming the sacrum. The sacrum articulates with the iliac bones of the hip bone to form the back of pelvis.
Coccygeal vertebrae: These are also called coccyx and are four vertebrae fused in adults.
It consists of twelve pairs of ribs. The ribs articulate posterior with the thoracic vertebrae. Ten ribs are connected interiorly with sternum either directly or through the costal cartilage. The rib cage provides support for a semi-vacuum chamber called chest cavity. The seven pairs of ribs that attach directly to the sternum are called true ribs. The 8th, 9th and 10th ribs are called false ribs, as these three pairs of ribs are attached to the sternum by means of common costal cartilage. 11th and 12th pair of ribs is known as floating ribs, because they do not attach to the sternum.
It consists of a pair of clavicles and a pair of scapulas.
Clavicles: These are a pair of collar bones forming the front of the pectoral girdle (shoulders). One end of each curved bone articulates with the sternum. The other end articulates with the scapulas.
Scapulas: These are two shoulder blades, triangular bones forming the back part of pectoral girdles. They do not articulate with ribs but are embedded in muscles. A depression called glenoid cavity accommodates the ball end of the upper arm bone. The other parts of scapulas are acromion for the attachment of muscles and for the articulation with the clavicle and coracoid process to which muscles of arm and chest are attached.
It consists of the following bones:
Humerus: Upper arm bone. Radius and Ulna: Forearm Bones.
Carpals: Eight short bones forming wrist.
Metacarpal: Five short bones forming the palm.
Phalanges: Three bones forming the fingers. Two bones form the thumb.
It is a long bone, the end of which has a spherical shaped head, which fits into the glenoid cavity, forming the shoulder joints. It has greater tubercle and lesser tubercle for the attachment of muscles. The shaft has many rough surfaces which give attachment to muscles; the most marked being the deltoid tuberosity. The lower extremity carries two condyles for articulation, with radius and ulna. Above the condyle on either side are processes called epicondyle, which gives attachment to the muscles.
Above the condyle there are two depressions the olecranon fossa at the back and coronoid fossa in the front.
Radius: It is a long, outer bone of the fore arm (on the thumb side). Its upper extremity is smaller and carries disc shaped head. Below the head is the neck and on the front of the bone, is a process called radial tuberosity for the attachment of biceps brachii muscles.
Ulna: It is a long bone on the inner side of the forearm, and slightly bigger than radius. There are two processes for muscle attachment. The processes are known as olecranon and coronoid processes. The olecranon is large and gives attachment to the triceps.
Carpals: These consist of two rows of four short bones. The upper row articulates with radius and forms the wrist joint. The lower row articulates with metacarpals of the palm.
Metacarpals: These consist of five bones making up the palm of the hand. The lower ends of the metacarpal bones form the knuckles which articulate with the phalanges or digits.
The pelvic girdle is the complete ring of the bone formed by the lower part of the back bone and the two hip bones.
(a) The hip bones are made up of three units the ileum, ischium and pubis which form coxa.
(b) The two halves of the pelvic girdle are joined at the pubic symphysis. A cavity called acetabulum is also present.
It consists of the following bones:
Femur: Thigh bone.
Patella: Knee cap
Tibia: Skin bone.
Fibula: Outer bone
Tarsal: Seven bones forming the ankle, heel and instep.
Metatarsal: Five bones making up the sole of the foot.
Phalanges: Three bones forming the small toes. Two bones form the big toe.
Femur: It is a long bone with head, which fits into the acetabulum. Greater and lesser trochanters are for muscle attachment.
Patella: It is embedded in a long tendon which runs over the knee joint. Its function is to ease movement of this tendon across the knee joint.
Tibia: It is the large bone in the leg. Its upper end articulates with the condyles of the femur, and the lower end articulates with the bones of the ankles.
Fibula: It is a thinner bone running down at the outer side of the leg. It joins the tibia just below the knee joint and just above the ankle.
Tarsal: It is made of seven bones which are tightly attached to form the ankle joint heel and instep.
Metatarsal: It consists of five bones which articulate with the tarsal and phalanges to form the sole of the foot.
Phalanges: These are the small bones which make up the toes on the same pentadactyl plan as the hand.