Question

Define joints and explain ball and socket joint with diagram.

Answer 1

Joint: The region at which two or more bones of skeleton come in contact and move freely is called a joint.

Ball and socket Joint: In such joints, one of the bones forms a cup like or socket like structure where the other forms a ball like structure which fits in the cup. The bone having a ball or head can move freely in the joint in a number of directions. Example of such joints are shoulder and hip joints.

A cartilaginous layer known as articular cartilage is present on the head of both the bones. The cavity present between the heads of both the bones is called synovial cavity which is filled with synovial fluid. A large number of muscle fibres or ligaments are present which keep these bones in their position.

These joints help in stretching or extending, folding or flexing addiction (towards midline) abduction (away from midline) and rotation of the limb.