Skeletal System In Human Body
Skeletal System in Human Body
Skeletal System in Human Body
Skeletal system constitutes hard internal or external living or non - living parts that form the supporting framework of body.
It is divided into 2 Parts :
Exoskeleton : It is hard, protective and supportive frame-work which is produced by ectoderm.
It is present on the outside of the body (made of either dead tissues or biochemical secretion).
Found in both invertebrates (shells of snails, corals, etc.) and vertebrates (hair, nails, claws, hooves, etc.).
Endoskeleton : It is hard, supportive framework which is produced by mesoderm.
It occurs inside the body and is made of cartilages and bones. Found in corals, echinoderms and vertebrates.
Divided into two main parts : Axial Skeleton and Appendicular Skeleton.
A. Axial Skeleton (Total 80 bones)
It lies along the principal axis of the body.
It includes skull, vertebral column, ribs and sternum.
Skull consists of two main parts - cranium and face.
Cranium (brain box) is formed by 8 bones and provides a bony protection for the brain.
Face : There are 14 bones which form the skeleton of face.
There are also present 6 ear ossicles in the skull.
Another bone is hyoid, which is horse shoe shaped present in neck between lower jaw and sound box (or larynx).
It supports tongue.
It is a string like vertebrae which lies in the mid dorsal line of the neck and trunk.
It is made up of 33 vertebrae in which 26 bones are visible because five sacral vertebrae are fused to form one sacrum and four coccygeal vertebrae are fused to form one coccyx.
It displays four curves to enhance balancing power and firmness for upright posture of body. The curvatures are cervical, thoracic, lumbar, pelvic (or sacral).
The vertebrae are grouped into five groups-cervical (7 bones), thoracic (12 bones) lumbar (5 bones), sacral (1 bone) and coccyx (1 bone).
Ribs are 12 pairs (12 x 2) of bony bars which form the sides of chest cage.
They protect the delicate organs (heart, lungs, etc.) and provide surface for attachment of muscles concerned with respiratory mechanism.
Sternum (or Breast Bone)
It is a narrow, elongated and flattened structure, present just under the skin in the middle of front of the chest.
B. Appendicular Skeleton (Total 126 bones)
This skeleton lies laterally and is attached to axial skeleton at an angle.
It is made up of girdles (pectoral and pelvic) and limb bones (forelimb and hind-limb).
Forelimbs: Consist of 60 bones
Hind - limbs : Consist of 60 bones
Pelvic Girdle : Has 2 hip bones.
Diseases of Skeletal System
Articulation of Bones the Joints
A bone joint or articulation may be defined as the junction of two bones.
The study of such joints is known as arthrology.
There are 3 principal types of bone joints.
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