The skin (cutis) is a generic cover the body surface reaches 1.5-2.0 m2. In 1 cm2 of skin contains 300 sensory nerve endings.
In addition to tactile features a protective skin, protecting it from damage located underneath the organs and parts of the body, prevents the penetration of harmful substances and microorganisms, and plays an important role in the process of respiration, water, heat transfer.
Some of these functions (primarily defensive) provided by the epithelial tissue (textus epitheliales), which covers the outer surface of the body and promotes the exchange of substances between the organism and the environment. Location on the border between internal and external environment protects the body from injury and infection control. Epithelial cells form layers, one side of which is in contact with the external environment, and the other is adjacent to the connective tissue. The blood vessels in them are not available, so power cells is due to the supply of nutrients from the underlying tissues. The shape of the epithelial cells squamous (flat), cubic and cylindrical. By the structure of the epithelium is divided into single layer, all the cells of which are located on the basement membrane, and multilayered, adjacent to the basement membrane only the inner layer and a typical skin epithelium. Multilayered epithelium cells are divided into keratinizing and neorogovevayuschy. The main feature of the epithelium is its high capacity for regeneration (recovery).
The superficial layer of skin called the nadkozhnitsey, or epidermis (epidermis), and a multilayered, constantly keratinizing epithelium. The thickness of the epidermis varies from 0.07 to 0.4 mm.
The epidermis consists of five layers of cells. The deepest, comprising 5-15 layers of cells is called a layer of granular or sprout. Several cells of this layer adjacent to proper skin called the basal layer (stratum basale), which creates new layers of the epidermis as the outermost layer orogovevaniya. In the sprout layer contains a pigment, that may influence skin color.
The next layer is called the prickly (stratum spinosum), and above it is a granular layer (stratum granulosum). The latter consists of a number of cells in the cytoplasm which contain keratohyalin. The fifth layer is called the vitreous (stratum lucidim), it is formed by rows of cells, and 3.4 is filled with brilliant material - eleindinom. The top layer consists of flat to form cornified cells and therefore is called the stratum corneum (stratum corneum). As a full orogovevaniya cells are transformed into flakes, exfoliate, and to replace them formed new ones.
The second layer of skin - the actual skin, or dermis (dermis), - is a fibrous connective tissue.
In interlaced with each other fibers lie muscles, blood vessels, glands, nerves, hair and nails.
In the dermis distinguish the deeper reticular layer (stratum reticulare) and superficial papillary layer (stratum papillae). On the surface of the papillary layer are arranged papillae, growing into the epidermis. In the grooves between the papillae are loops of blood vessels and nerve endings, which, together with a mesh layer nerve endings are the receptors that perceive tactile stimuli. Smooth muscle tissue contained in the dermis, forming the muscles that raise the hair (mm. arrectores pilorum). Due to their reduction is an allocation of the secret of skin glands and the appearance of "goose skin."
|In Fig. 294.
1 - the hair shaft;
2 - it's time to sweat;
3 - duct sweat gland;
4 - the muscles that raise the hair;
5 - sebaceous gland;
6 - a root hair;
7 - the hair follicles;
8 - papilla of hair;
9 - bag of hair (follicle);
10 - sweat-gland
Between the epidermis and the skin itself is the main membrane fuses with the basal layer. Dermis smoothly into the subcutaneous tissue (tela subcutanea), which contains loose connective tissue with fat cells, through which the skin can move and corrugate. On the palmar surface of hands and soles of the feet are places where large amounts of fat, nerves, and the dense connective tissue. They are called tactile ridges (toruli tactimg).
a., aa. — arteria, arteriae (artery, the artery)
lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)
m., mm. — musculus, musculi (muscle, the muscle)
n., nn. — nervus, nervi (nerve, the nerve)
r., rr. — ramus, rami (branch)
s. — seu (or)
v., vv. — vena, venae (vienna)