Hair Structure

The growing part of the hair lies within a tubular indentation of the skin called the follicle. The bottom of the follicle is penetrated by a small upward-growing projection of connective tissue called the papilla, on which the hair bulb is formed. The part of the hair inside the follicle is the hair root. The part outside is the hair shaft. Popularly in tinting we speak of "root" as hair adjacent to scalp.

Each hair follicle is supplied with one to six sebaceous or fat-produc­ ing oil glands. Their function is to supply an oily wax of butter-like consistency to lubricate the hair and give it luster and to protect it from dry atmosphere. Decreased secretion causes dry hair, while over-func­tioning causes seborrhea and oily hair and skin. Less wax is excreted in cold weather. Children have less oil in their hair than adults. The oily excretion increases sharply in puberty and the last months of pregnancy and on a diet especially rich in carbohydrates and fats. With progressing age, the secretion decreases, causing dry scalp and hair so common in later years. The decrease in the secretion occurs in women at about the age of 40 and is much slower in males.