Structure Of The Hair

2. Structure Of The Hair

All mammals possess hair of some kind. Like the nails and the many sudoriferous (sweat) and sebaceous (oil-secreting) glands, the hair is considered to be an appendage of the skin (something which is considered a proper part of a greater whole). Some animals have smooth hair, some stiff bristle-like outgrowths; still others, pointed spines.

Individual hairs are composed chiefly of a rather horny substance, a sclero-protein, a simple protein known as keratin. The amino acids of which keratin is composed are strung together in a more or less straight line, one after another. These lines of amino acids are called polypeptides. Keratin is a fibrous protein and fibrous proteins are strong, sturdy, and tough. This same kind of protein is also found in the fingernails and toenails.

In humans the hair consists of a cylinder 1/400th inch in diameter. At the base of the cylinder, which consists of a shaft and a point, there is a “root” which is embedded in the skin in a kind of pouch-like depression called the hair follicle. Beneath this depression is the papilla, a kind of nipple which fosters the hair and builds new hair cells. The papilla might be called the “connecting link” between the hair, the blood, and the nerves which service it.

The shaft or outer part is pithy (called medullary substance). It is surrounded by a fibrous part containing pigment and this portion is, in turn, covered by a layer of epithelium scaly cells. Near the point, the pith begins to taper off to form the penetrating point of the hair shaft.

In humans the hair begins to develop in the fetal period. By the sixth month, the tiny fetus is literally covered with fine hair which is termed the lanugo. Following birth, the lanugo is rapidly shed and is replaced by hair in all the familiar places and in rather precise forms: coarse hair over the cranium and eyebrows and fine, downy-like hair over the rest of the body, the latter often being so fine as to be almost invisible to the naked eye:

At puberty certain changes are evidenced. Coarse hair begins to develop in the armpits and over the pubic or groin area in both males and females. In males the hair begins to grow more coarse over the upper lip and about the lower portion of the face and, if unshaved, quickly forms a beard.

The rate of growth of the hair varies according to age, health of the individual, and the length of the hair. When hair is cut short, for example, it can grow as much as 3/4ths of an inch and even more in a month but by the time it is 12 inches in length, its rate of growth can be reduced by as much as one-half, all other things being equal, of course.

The hair of young people grows faster than that of older people, with the fastest growth being found in women, especially from 16 to 24 years of age, this latter age being about the time when most humans are said to reach full maturity.

The type of follicle determines the identifying characteristics of the hair in different races. The black woolly hair of Blacks, Papuans, and Melanesians grows from a curved follicle which imparts a spiral twist to the hair. This kind of hair growth appears flat or tapelike when cross-sectioned and viewed microscopically.

The characteristic straight, coarse, long, and almost always black hair of the Chinese, Japanese, Eskimo, and American Indian grows from a straight follicle and this type of hair is round in cross section and possesses a plainly visible pithy center.

The hair of other group types, including those of European ancestry, is often wavy and somewhat intermediate in texture between the straight and woolly types. This latter kind of hair also grows from a straight follicle, but it is oval in cross section, this shape giving it a greater or lesser tendency to curl.

Variations in pigmentation among this last group causes the hair to exhibit a wide range of color from light blonde to various shades of red to black.

Hair grows on the human body where protection is needed. It serves to protect the head area where is housed the control center for all metabolic activity within the entire organic community. It protects the individual from the heat of the sun and from the cold of nights and frigid winters. Body hair helps to retain the heat of the body. When located in ingress passageways as, for example, in the nose and ears, the hair prevents the entrance of foreign matter into the nose, lungs, ears, and other possibly accessible parts.

The hair on the head helps to preserve the brain and nerve centers from shocks, injuries, and irritation from harmful external influences; from blows, for instance. The hair is an organ of touch. It is extremely sensitive and responds quickly to danger. Hair has been observed to stand on end from fear, anger, or when the head has been dealt a blow.

Extremes of heat are believed to induce more rapid growth of the hair than moderate temperatures. This may be due to a kind of incubating effect.

Dr. St. Louis A. Estes, in his book Raw Food and Health, gives the following analysis of hair substance:

and goes on to point out that blonde hair contains lesser amounts of carbon and hydrogen and greater amounts of oxygen and sulphur.

Brown hair, on the other hand, has more carbon and a small amount of oxygen and sulphur, interestingly enough white hair contains high quantities of calcium phosphate. In white hair the pigment ratio is reduced and the pigment replaced by tiny air bubbles.