Like the skin, hair is an important part of the body's defence system. Its various functions are determined by its location on the body and to what extent that part of the body is exposed to potential invaders. The hair on our bodies originally protected us from excessive cold and from harsh elements. It has largely lost these functions now and principally serve4s to capture dust and small insects which would otherwise have easy access to the body through the ears, nose and eyes. The hair on our arms and legs serves to warn us of danger or sudden cold. The coarse hair which forms the eyebrows not only protects the eyes from foreign bodies but also stops perspiration dripping into them. The hiar on our head protects us from loss of body heat and from potentially toxic elements in the air which might otherwise find their way into our circulation.
Hair follicles (or sheaths) form on the newly developing foetus between the second and fifth month. The root of the hair starts to grow inside this 'container'. This root is in fact the only part of the hiar that is alive. The hair is simply a stack of dead cells in a long tube shape that have been pushed up by the new cells growing from the root. Every hair is at a different stage of growth and development to its neighbour. If you run your hand over your scap you will feel soft new hair growing alongside older and thicker hair.
Special nerve endings beneath the skin cause tiny muslcles attached to each hair follicle to contract and the hair to stand on end. This response can be activated by the hormone adrenalin. In an emotional state such as fear or hostility, or a sudden change in temperature from warm to very cold, the muscle will contract in order to conserve body heat in case it should be needed for sudden action. The pull of the muscle makes the hair stand erect and makes a dent in the skin where the other end of the muscle is attached. This causes the condition we know as goose bumps.
Baldness is a medical mystery. We do know that certain types of hair loss can be set off by intense emotional shock, by an illness or pregnancy ; but the most common type of baldness, that seen in maturing males, remains largely unexplained. It is not due to wearing hats too often, too tightly or not enough. It is in part genetically transmitted, but mysteriously almost always overlooks women.
Some Amazing Hair Facts :
The average human has as much hair as the hairy primate, but it is so short and fine we simply do not look as well covered.
An average human head is covered by about 100,000 strands of hair.
Each ordinary hair has a life span of about three years, eyelashes live about 150 days.
The soft down-like hair of the newborn sometimes reappears on the body of the aged.
A swami in Madras (now Chennai), India, was found in 1949 to have hair nearly 26ft long. Normally, hair which is not cut grows no longer than 3ft.