JOINTS AND MUSCLES

We can perform a wide range of movements thanks to the joints in various parts of our bodies. The type of joint varies according to the job it has to do. Try swinging your arms round. It is quite easy, because there is a ball and socket joint at the shoulder. You cannot move your knee in the same way; the lower leg can only move up and down, because the knee has a hinge joint.

To move our limbs, we need muscles as well as joints. There are over 600 muscles in the body. Muscles are attached to the bones by tendons, and pull on them by contracting. The large number of joints at the wrist allow movement in many directions. The flesh of the body is made up of muscles which are attached to bones. Over half the weight of the body is muscle. Muscles work in pairs. The diagrams show this happening in the arm. When the biceps muscle relaxes, the triceps muscles contracts, pulling the forearm down or vice versa.