Skeleton - Movement and Locomotion

1. The human skeleton:

(i) The framework of bones and cartilage that protects our organs and allows us to move is called a skeleton or skeletal system.

(ii) The human skeleton performs many functions such as support, protection, movement and locomotion, blood cell formation, storage of minerals and storage of energy.

(iii) The human skeleton in an adult consists of 206 bones.

2. Divisions of human skeleton:

(i) The human skeleton is divisible into two parts - axial skeleton and appendicular skeleton.

(ii) The part of the skeleton that lies around the body axis is known as the axial skeleton. It consists of a skull, vertebral column and ribcage which protect delicate organs like brain, spinal cord, heart and lungs.

(iii) The axial skeleton consists of the bones that form the upright portion or axis of the body, i.e., skull, hyoid bone, ear bones, vertebral column and sternum. There are 80 bones in the axial skeleton.

(iv) The appendicular skeleton consists of the bones of the free appendages - upper and lower limbs, and the bones (girdles) which connect the limbs to the axial skeleton, i.e., pectoral and pelvic girdle.

3. Joints:

(i) A joint is a point of contact between bones; cartilage and bones and teeth and bones.

(ii) On the basis of functions, joints can be classified as immovable, slightly movable and freely movable.

(iii) On the basis of structure, the joints can be classified as fibrous joints, cartilaginous joints and synovial joints.

(iv) Fibrous joints are the joints in which there is no synovial cavity and the bones are held together by fibrous connective tissue.

(v) Cartilaginous joints are the joints in which there is no synovial cavity and the bones are held together by cartilage.

(vi) Synovial joints are the joints in which there is a synovial cavity and bones forming the joint are united by a surrounding articular capsule and accessory ligaments.

(vii) Synovial joints can further be classified into hinge joints, pivot joint, gliding joints, ball and socket joint and saddle joint.

(viii) The hinge joint is a joint in which the convex surface of one bone fits into the concave surface of another bone and movement is primarily in one direction or in a single plane only.

(ix) Pivot joints are the joints that allow rotation around an axis, i.e., neck and forearms.

(x) Gliding joints are the joints in which the articulating surface of the bones are usually flat and one bone slips over the other.

(xi) Ball and socket joints are the joints in which ball-like surface of one bone fits into a cup-like the depression of another bone, and movement is primarily in three planes of motion.