Hair

Hair - appendages of the skin that covers almost all of the skin. Hairy missing only on the red border of the lips, palms, soles, back surface of third knuckle, as well as on the nipple, the head of the penis, the inner leaf of the foreskin, on small labia and inner surface of the labia majora.
There are lanugo, covering the entire body, bristly (eyebrows, eyelashes), long hair ( head, pubic, genitals, in the armpits). In hair distinguish rod protruding above the surface of the skin, and located in a thicker skin root ended hair bulb (Fig).
hair cuthair shaft (Fig., 1 and 4) consists of three layers: the deep - brain substance, which consists of not fully dead epithelial cells; the average, constituting the bulk of the hair, the cortical layer (formed the horn cells) pierced fibrils and contains a pigment that determines the color of hairs; outer layer - cuticle - consists of one series Horny plates, located laid.
The root of the hair with the hair bulb (Fig., 7) concluded in the hair follicle, consisting of connective and epithelial inner and outer sheaths (Fig., 6), Connective tissue of the vagina (the hair bag; figure, 5) developed only in the lower part of the root. The outer epithelial vagina is a continuation maleyeva layer of the epidermis, which, estancias to 2-3 rows of cells, merges with the cells in the hair follicles. Internal epithelial vagina is formed from cells bulbs; in it there are three layers: the outer layer of Henle, consisting of one row of cornea plates; inner-layer Huxley, consisting of 1-2 layers of cells containing a kind of grainy and orogovevshi in the upper sections of the vagina; the cuticle, similar in structure to the cuticle of the hair.
In the hair follicle into the excretory duct of the sebaceous glands. Each hair follicle (except bristly hair) provided with a bunch of smooth muscle that raises hair (Fig., 3) and contributing to the emptying of the sebaceous glands (Fig., 2), In the hair follicle juts out connective tissue papilla (Fig., 8), richly supplied with blood vessels, going from deep vascular network of the dermis, and nerve fibers. Hair follicles are also equipped with plexus nerve fibers, which are located mainly in the connective tissue of the vagina and the circular of the cervix of the follicle.
Trophic function in relation to the hair is carried out not only by the nervous system, but hormones of some endocrine glands (pituitary gland, thyroid gland, sexual glands).
Hair growth is due to the multiplication of cells bulbs (matrix)containing a large amount of pigment. Hair length is increased in a month on the average on 1 see the life Expectancy of the hair on the head 2-4 years, after which it is replaced by the new. This stops the multiplication of cells bulbs, they coarsen and together with the old hair rise up to the mouth of the follicle of the hair falls out. The process of regeneration begins with a reproduction of the epithelial cells of the outer vagina, which, covering papilla, form a new matrix.
Diseases of the hair and hair follicles - see Alopecia, Fungal diseases of the skin, Pyoderma.