Page 2 - CH-8 -8.4 JOINTS

 JOINTS

 The places where two or more bones meet are called joints. The bones are
held together by a special tissue called the ligament.
 For example: our arm bends at the elbow, our legs can bend at the knee
and our head can rotate around our neck. These junctions are known as
joints.
 When bones move at the joints, they rub against each other. If the bones

kept rubbing against each other over a long period, they would wear out.
Therefore, to prevent the bones from wearing out, there is a presence of
soft, flexible and elastic tissues called cartilage which covers the ends of the
bones where they meet to form a joint.
 The tip of our nose and the outermost part of our ear are soft due to
presence of cartilage.
 Joints are present at different places in our body. They are of two types –
1. Movable joints

2. Immovable joints

1. MOVABLE JOINTS

 The joints where the joined bones can move are called movable joints.
 In such joints, a lubricating fluid is present between the bones, which allow
them to move smoothly.

 In our body, 4 types of movable joints are present and these are:
I. (a) Ball and socket joint
II. (b) Hinge joint
III. (c) Pivot joint
IV. (d) Gliding joint.

I. BALL AND SOCKET JOINT

 The rounded ball-shaped end of one bone fits into cavity or socket (hollow

space) of the other bone is called ball and socket joint.
 Such joints allow movements in all directions.
 Examples: shoulder joints, hip joints.