Support And Movement In Man (Biology-Lesson-14.6) Part 4

14.6.7 Defects of skeleton system

(a) Changes in bones

Bones become thinner, weaker and less flexible with aging. This is partly because required calcium level starts decreasing at the age of 34 years. This happens to every-body to some extent. In some people it is particularly serious. In such cases it results in a condition known as osteoporosis or softening of bones.

Although whole of the skeleton is affected by osteoporosis yet hips. Wrists and vertebrae tend to be affected worst of all. Even a minor fall can result in broken bone.

Fig. 14.22 (i) ball and socket joint (ii) hinge joint

Fig. 14.23 scanned electron micrograph of brittle and spongy fractured femur from a patient with osteoporosis. The dark areas show the affected portions of the bone.

Apart from the fractures, weaker bones in the spine may result in the:

Compression in the bones and intervertebral discs. Loss of height.

Collapse of vertebrae causing bending of spine.

Note: Osteoporosis or softening of bones is most common in elderly women affecting about I in 4 over the age of 60. A balanced diet rich in calcium and regular exercise helps to keep bones strong.

(b) Changes in joints

The load bearing joints such as knees and hips particularly show changes. Like fingers joints, they become stiff and painful.

1. Osteoarthritis is a complex joint disorder (fig 14.24). As ageing progresses, the smooth tough cartilage which covers the ends of bones at joints becomes weaker and less extensive. It gradually breaks down. In extreme cases, the ends of the bones may become exposed. They start to grate against each other. This results in swelling and deformation of joints.

 

Note:  A less frequent type of joint degeneration known as rheumatoid arthritis is common in older people than in young people. It is an auto-immune disease in which body’s immune system attacks its own tissues. Affected joints become hot and swollen during attacks.

2. In some cases membrane of the joints become thick. The joints swell and become stiff causing pain.
3. Some times excessive use of protein may result in the deposition of uric acid at joints causing swelling and pain.

© Dislocation of joints

This is the displacement of one more bones at a joint, caused by injury and sometimes by muscular action.

A severe sickening pain, abnormal appearance of joint along with swelling shows the dislocation of joints.

Fig. 14.24 a severe case of osteoarthritis in the left knee of a man showing the swelling and deformation of joints.

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