Sebaceous glands

1 - a sebaceous gland;
2 - the hair follicle

Sebaceous glands - alveolar glands of the skin that produce sebum. Almost all of the sebaceous glands open in hair follicles, only on the head of the penis, the foreskin, small private parts lips, nipples, in the skin of the lips at the corners of the mouth they open directly onto the surface of the epidermis. Sebaceous glands are still simple branched alveolar glands (see) and consist of secretory Department and short ductless. Secretory Department deprived cavity and consists of several layers of cells. Germ layer, multiply, replenish the loss of the overlying cells. In the latter happens rebirth of cytoplasm in fat. Transformed cells are destroyed, and enclosed in them fat together with the remains of dead cells forms a secret of sebaceous glands - sebum (see Skin physiology). Pathology of the sebaceous glands - see Adenoma of the sebaceous glands, sebaceous cyst, Seborrhea.

Sebaceous glands (glandulae sebaceae) - alveolar glands of the skin with gologanov secretion that produce skin oil (sebum). Almost all of the sebaceous glands open in the hair follicles. In a red border and the mucous membrane of the lips, in the edge of the century (meibomian gland), around the nipples, genitals and anus are sebaceous glands, opening yourself to the skin surface (available S. W.).

large and small sebaceous glands scheme
Fig. 1. Large and small sebaceous glands (scheme): a - large sebaceous glands in the skin of the scalp; b - cheeks; in - nose; g - small lanugo with the embryo of the sebaceous glands; a - small vellus hair with small sebaceous gland. 1 - epidermis; 2 - dermis; 3 - the subcutaneous cellular tissue; 4 - hair follicles; 5 - the sebaceous glands; 6 - sebaceous tube; 7 - muscle lifting the hair.

Sebaceous glands that in the hair follicles, divided into large and small (Fig. 1). The beginnings of the big C. W. as outgrowths on the hair follicles appear with 3-4 month fetal life (secretion begins on 6-7 months). The beginnings of small C. W. formed at the end of antenatal and early postnatal periods. Free sebaceous glands develop later. The secret S. W. lubricates the skin and hair, gives softness and elasticity, protecting them from drying out and harmful effects. Fat grease the fetus (vernix caseosa) protects the skin from maceration amniotic fluid and easier it passes through the birth canal. The main components of sebum - lipids (with a high content of cholesterol) and proteins. The total amount allocated by the skin fat according to different data is from 1 to 2 to 20 grams per day.
Are the sebaceous glands of the excretory duct and secretory Department (Fig. 2). On the periphery of the latter are rich in enzymes small cambial cells, and in the center - large cells at different stages of fatty degeneration. The disintegration of these cells and produces sebum. Separation takes place by pushing at the mouth of the hair follicle units secret newly formed portions and in case of compression C. W., for example, when the movements of the body, muscles, skin, etc. Thin connective tissue sheath S. W. contains argyrophile fiber and neutral polysaccharides. S. Zh. well vascularity and are sympathetic innervation.
The function of the sebaceous glands is closely linked to hormonal influences.
The number and value of C. W. in different parts of the body differently. There are also individual, sexual and age differences. Most S. W. in the scalp (especially on the face), in the distal direction their number is decreasing. In the skin of the palms and soles S. W. no. Total C. W. 1 cm2 surface in the skin of the forehead 2.4 mm3, back to 1.5 mm3, hips 0.5 mm3 and Shin 0.03 mm3.
In most areas of the skin are simultaneously both large and small, S. W. (the latter is significantly less). Large sebaceous glands are usually associated with large (long and bristly) and large vellus hair. Secretory departments (sometimes excretory ducts) are often very extensive (simple and complex Mnogotochie S. W.). Secretory departments lie in the middle and lower thirds of the dermis, they implemented contains the capillaries and connective tissue layer and nipples. In some areas of skin, especially in the skin of the nose, sebaceous glands reach the largest sizes. Related hair since the end of the life of the fetus begin gradually be transformed into a fine vellus and become appendages of the sebaceous glands, and the upper part of the hair follicles become the continuation of the excretory ducts S. W. In extended channels secret often hardens and turns into a grease caps. Small C. W. associated with vellus hair, often deprived of the excretory duct and have usually unbranched or maaratlemine secretory departments (simple one-, dodelete S. W.). They are, as a rule, in the upper third of the dermis. Part of lanugo hair S. W. throughout life remain in the form of germs. Cm. also Cancer.

Fig. 2. A sebaceous gland opening in the cuticle (follicles): 1 - the ground clearance of the hair follicle; 2 - the hair shaft; 3 - excretory duct of the sebaceous glands; 4 - desquamated dying cells; 5 - a sebaceous gland.