Hair

From Encyclopediak

Hair, a part of the protective covering of Mammals. It is variously distributed over the body and corresponds with the feathers of birds, scales of fishes and of reptiles. It takes the form of wool and fur or bristles and quills, and presents variations of color equally diverse. Because of the delicate structure and important function of the brain, the human head is abundantly supplied with hair to cover necessarily exposed or thinly covered parts. Each hair of the human head springs from a depression in the skin, called the hair follicle. It consists of a stem and a bulb-shaped root, which rests upon a minute elevation, or papilla, of the skin at the lower end of the follicle. A hair is made up of a number of elongated epidermic cells united to form fibers. These cells multiply rapidly in the papilla and, pushing upward, force along the older cells. It is in this manner that hair grows. If the reproductive organ at the base of the root be destroyed, as is often the case when hair is pulled out, growth is no longer possible. Death of all the papillae of the head, often caused by poor circulation of the blood in the scalp, results in baldness. Extending from the side of each hair follicle to the skin surface is a slender bundle of unstriped muscle, its oblong direction causing the hair to lie close to the head. Emptying into the follicle are sebaceous, or oil glands, one or more to each follicle, which lubricate and soften the hair. Hair is an important article of commerce, sheep's wool being the most valuable. The hair of camels, goats and alpacas is used in combination with cotton and wool in the manufacture of dress fabrics. Hog bristles are used for making hair brushes, while the fine brushes of painters are made from the hair of sable and marten. Hair used for making wigs comes largely from the heads of European peasants.