Hair follicles are distributed in variable quantities over the entire surface of the skin, with the exception of certain regions (palms, soles, lateral surfaces of the fingers, lips, external genital organs). They are structurally complex, including the hair in its connective tissue sheath, the arrector muscle, the sebaceous gland, and in certain regions, an apocrine sweat gland.
Each hair on the body, which has much of the same biological machinery as the hair on the head, has a sebaceous gland attached to it. They contain sebocytes, cells whose function is to produce the lipids that constitute the skin’s sebum. The sebum is transferred by the sebocytes into the duct of the sebaceous gland and is then secreted onto the surface of the skin where it mixes with sweat to form the hypodrolipidic film. This fiml acts as a lubricant that protects the skin from small scratches, harsh treatment and drying out, and also prossesses antifungal properties.
There are two types of sweat glands : eccrine and apocrine. Eccrine glands are very abundant on the soles of the feet, the palms of the hands and the armpits (600/cm2), and they secrete a transparent fluid composed mainly of water, lactic acid, urea, toxins arising from metabolism and even substances which fight against bacteria. The main function of this eccrine sweat is to cool the body : it eliminates by perspiration the excess heat. Apocrine sweat glands are situated in specific areas : the armpits, the eyelids, the pubic area and the genitals. Their secretion is more opaque, thicker, and richer in fats, cholesterol and fatty acids. These substances can be broken down into unpleasant smelling substances by bacteria on the skin surface.
Nails consist of a quadrangular, flexible plate composed of keratin, covering the dorsal surface of the fingers.