Physical Fitness and Well-Being and Care Hair Part 1

About physical fitness, medical information, trivia, anatomy, well-being and care of hair.

TAKING A PHYSICAL--HEAD TO TOE

HAIR

Medical scientists have apparently not been sufficiently interested to count the number of body hairs the average person has over his or her body. But it has been estimated that the average person has about 100,000 scalp hairs.

Each hair grows from a papilla, or bulb-shaped root, planted slightly below the surface of your skin.

A single hair has three layers: the cuticle, or outermost layer, made of thin cells which lie one over the other like scales; the cortex, which gives the hair its form and body, as well as its color; and the medulla, the innermost core, which does not usually extend to the end of the hair.

The hair grows from a sort of sheath in your skin, known as a hair follicle. Follicles are usually set at a slight angle, which accounts for the direction in which your hairs point.

Each hair follicle has a tiny muscle attached, which contracts when you are cold or excited, causing the hair to stand on end.

Hair grows, on the average, 1.5 to 3.0 millimeters per week.

The growth patterns of hair vary greatly over your body. For example, scalp hairs live from two to five years; eyebrows and eyelashes, from three to five months.

If you examined cross sections of hairs, your would find three types: round hair shafts for straight hair: kidney-shaped hair shafts for wavy hair; and oval shafts for curly hair.

All sites for hair follicles are established when you're born. You do not grow new ones after that, though the color and size of the hairs growing from these follicles will change.

Normally, you lose from 30 to 100 hairs each day from your scalp. New hairs then grow in their places.

Hair grows in cycles. There is a growth period, followed by a rest period. For most adults, a scalp hair will grow for three years, then rest for three months. After this the hair loosens and falls out, and a new hair grows from that follicle.

Hair color is produced by a pigment in the cortex layer of the hair. This pigment originates in the hair follicle.

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