Answer
All body tissues and system are affected by the process of aging and the results get more noticeable after the age of 50. In general, there is loss of water and there is shrinkage in connective and epithelial tissues, There is insertion of cholesterol molecules between protein molecules of the plasma membranes, and this is inimical to flexibility.
Work Step by Step
In the skin the number of melanocytes decreases, fibroblasts produce abnormal disorganized collagen fibers, and elastic fibers lose their elasticity, thicken, and break. The numbers of sweat and sebaceous gland decrease; there is hair loss ; skin wrinkles.
Bone mass decrease progresses with aging; there is demineralization , and loss of bone protein resulting in bone brittleness and increase in fractures. Articular surfaces of bones lose their covering of cartilage; spurs develop on vertebrae; the spinal canal narrows( stenosis), and ligaments shorten.
Skeletal muscle mass decreases from 10 to 50% as aging progresses ; fibrosis develops in muscles; adipose tissue replaces muscle; flexibility decreases, and reflexes slow.
In the endocrine system the production of growth hormone, parathyroid hormone, and thyroxine decrease, but thyroid stimulating hormone and calcitonin production increase. Insulin activity slows, but hormones of the adrenal medulla--epinephrine and norepinephrine-- are scarcely affected. Changes in the production of sex hormones are complicated by sex and changes in life, but they are substantial and far-reaching.
