Anatomy of the skin

Restricting internal organs from the external environment, the skin (the "roof of the body") is not only a mechanical case, a shell. Its various cells form a connective-tissue covering, which is the largest specialized organ of man. The area of ​​the skin is 2 m, the thickness varies from 0.5 to 4 mm, the mass is almost 3 kg, about 70% is water and 30% is proteins (collagen, elastin, reticulin), carbohydrates (glucose, glycogen , Mucopolysaccharides), lipids, mineral salts (sodium, magnesium, calcium) and enzymes.There are folds, grooves and ridges on the surface of the skin that intertwine and form an individual pattern.It is unique (from six months of pre-natal life to its very end) On the surface of the phalanges of the fingers, which is used to identify the person in judicial practice (fingerprinting).
The skin is stretched, elastic, resilient, which is due to its properties and fatty tissue, fasciae, bones, to which it is attached by connective tissue strands. Color depends on the coloring matter - the pigment and the degree of blood filling of the vessels. In the skin is a large number of sebaceous and sweat glands. Almost all of its surface is covered with hair (down), which together with glands and nails are called appendages of the skin.
Microscopically distinguish three layers: epidermis (cuticle), dermis (actually the skin) and hypodermis (subcutaneous fat tissue).
Epidermis - the surface layer of the skin. There are 5 zones (layers) of cells, different in shape, size and functions: 1) horny, 2) shining, 3) granular, 4) prickly, 5) basal. The epidermis is renewed due to its deep layers, which, as they approach the surface, gradually undergo structural and biochemical changes and become flat (keratinized by them).
The basal layer consists of cells that are functionally heterogeneous. Some relentlessly reproduce the synthesis of protein for the formation of new cells, others synthesize the pigment of the skin. Normal skin coloration depends on hereditary and external factors - the formation of pigment is stimulated by the action of ultraviolet rays.
The cells of the prickly zone, like the basal, are capable of reproduction and are combined together under the name of germ cells. In this zone there are also "white" cells wandering between the dermis and the epidermis, participating in the immunological defense of the organism.
In the granular layer, located above the spiny, there are numerous grains, indicating the beginning of the keratinization process.
A brilliant layer, clearly visible on the palms and soles, is diffusely impregnated with a proteinaceous substance, which subsequently turns into the final product of keratinization - the protein keratin.
The stratum corneum is directly in contact with the external environment and consists of flat keratinized cells (scales), closely connected to each other.
The most powerful horny layer is on the soles and palms, on the face it is thinner than all. The most superficial horny scales constantly disappear - slushchayutsya that has age and seasonal differences.
In the dermis (actually the skin) are the blood and lymphatic vessels, nerve endings, sebaceous and sweat glands, hair roots. The thickness of the dermis is from 0.5 to 5 mm, the largest on the back, shoulders, hips. In the dermis there are also smooth muscle cells, which in places form small bundles. They braid the hair follicles (sacs) and are called the muscles of "lifting hair." Other bundles are located on the skin of the neck, forehead, back of the hands and feet. Reducing them, reducing the flow of blood, causes the appearance of "goosebumps," thereby regulating the heat transfer of the body.
The thickness of fatty tissue is not the same. In the region of the forehead and nose is weak, on the eyelids and skin of the scrotum is completely absent, on the stomach, buttocks and soles reaches a few centimeters. The fat layer softens the effect of various mechanical factors, provides mobility of the skin, is a good thermal insulator. It contains blood vessels, nerve fibers, sweat glands and hair.
Mucous membrane of the mouth received its name from the fact that its surface is constantly covered with mucus. The keratinization is observed only at chronic inflammatory processes (for example, red flat deprive, a red lupus). The secret of the salivary glands is involved in the digestion of carbohydrates of food. The moistened by it epithelium of the oral cavity is able to pass into the underlying blood vessels many medicinal substances. It is used in medical practice with sublingual (under the tongue) administration of medications, for example, validol. The nervous apparatus of the oral mucosa is a vast network of motor, sensory and taste receptors associated with the sublingual, glossopharyngeal and vagus nerves.