What is the epidermis? Structure of the epidermis

The outer covering of the body has a rather complex structure. Skin is an organ that consists of two layers. It performs a number of important functions: exchange, heat-regulating, receptor, protective. Many are interested in what the epidermis is, but forget about the second component of the skin - the dermis.

Structure of external body cover

The skin consists of two layers - the epidermis and the dermis. The upper epithelial layer is separated from the lower by an uneven, wavy line. Its appearance is caused by the presence on the surface of the skin of special outgrowths - papillae. Its upper layer is a stratified planar multilayered epithelium. There are no blood vessels in it, and food comes to it only from the dermis.

Having dealt with what is the epidermis, finding out where it is located, many begin to be interested in its structure. It consists of cells, different in shape and structure. They reflect certain phases of their life. The thickness of the epidermis, depending on the location of its location can be from 0.07 mm to 1.4 mm. The thickest layer is on the soles of the feet, palms. And the thinnest skin (its upper layer) is in the pubic region, on the forearms, the ear shells and the abdomen.

Structure of the upper stratified corneum

The epidermis consists of 5 separate layers. Its main component is called keratinocyte. But the structure of the epidermis is more complicated than it may seem at first glance. Specialists distinguish such layers:

• Basal (embryonic);
• Spiny;
• grainy;
• brilliant;
• horny.

Each of them performs special functions and has its own structure.

It is important to know that the epidermal cells are in a state of constant renewal. In the layers are the processes of reproduction, movement, keratinization and sluschivaniya. Depending on the specific part of the body, the process of complete renewal of the epidermis can take from 20 to 30 days.

The stratum corneum

The upper part of the epidermis consists of cells that are close enough to each other. The components in the stratum corneum are an epidermal cutaneous barrier - they are called corneocytes. These epidermal cells already lost cell organelles and were filled with keratin.

Due to this, these horny components of the layer can protect the underlying tissues from mechanical damage, temperature fluctuations, drying and penetration of bacteria. Horny scales are divided into two types. They can have loose or dense filling of keratin fibrils. On the surface are the second ones. And the first are located closer to the granular layer. In their structure, it is possible to detect residues from previously existing cellular organelles. These scales are often called T-cells.

This top layer of the epidermis is a cutaneous barrier and consists of several layers of already dead cells that are impregnated with lipids. By the way, these substances are the main custodians of moisture in the skin.

Brilliant layer

This part of the epidermis is not always expressed. It is also called the eleidin layer. If it can be found, it looks like a thin, bright, bright and uniform strip. The layer was named only because of its appearance. Its component is a substance called eleidin. It is the product-base for further keratinization of cells. It is found, as a rule, only in the skin of the soles and palms. It consists of denuded flattened cells.

Granular layer

Those who understand the epidermis, find out where it is and remember its thickness, understand that each of its components is negligible. So, the granular layer consists of only 1-2 rows of cells in those areas where the thin epidermis. But it can consist of 10 rows of cells in places where the skin is more dense. They are rhomboid, elongated, elongated, and closely pressed against each other. The cells in this layer have already lost their ability to divide. In their cytoplasm there are two types of granules: lamellar and keratogialin. They are located so that the long axis of each rhomboid cell is parallel to the groove or scallop stroke.

Thorny cells

Regardless of the location of the skin area, this layer consists of 5-10 rows. The cells in it have the form of polygons. When viewed under a microscope, you can see not only the layers of the epidermis of the skin, but also to see the cells themselves, the narrow strips of space between them and the thin processes that cross it. Due to their presence, the layer was called spiny.

Keratinocytes are connected in this part of the epidermis by desmosomes. They have a rather complex structure: they look like 2 plates, and between them are alternating between themselves 4 electron-transparent and 3 electron-dense layers. It is desmosomes that support the internal structure of cells, they are the guarantor of a strong intercellular connection. They also serve as an attachment point for tonofilaments. It should be noted that the human epidermis is arranged in such a way that the amount of desmosomes decreases in the upper sections of the spinous layer.

The structure of the cells resembles the components of the basal department. But at the same time they are different. Thorn cells are connected by a significant number of desmosomes, and the bundles of tonofilament are thicker.

Basal cells

This layer is the most distant from the surface of the skin. But he gives the full opportunity to understand what the epidermis is. The last layer on the basal plate is located, which limits it from other tissues. The cells in it are arranged in one row. The layer that they form is also called the embryo. There are several types of cells. There are keratinocytes, melanocytes, lymphocytes, basophils of tissue. Also in the layer are the cells of Greenstein and Merkel.

Keranocytes in this layer look like cylinders, which stand vertically. They are distinguished by 2 types: with a flat and serrated surface. The first of them are divided, due to them there is a change of cells. The second perform a backup function. But with any skin damage, they begin to actively share.

Completely understand and understand how the structure of the epidermis is arranged, if you know that the structure of the constituents of the basophilic layer is slightly different. In addition to organelles and nuclei, which are typical of all other cells, they contain specific structures - tonofilamenes. Also there are special inclusions, which are called melanin granules.

Separately it is necessary to say that melanocytes are special cells capable of producing melanin. This substance protects against the damaging effects of ultraviolet radiation. In the basal layer is about 10-25% of these cells. By appearance they resemble a sea urchin and are located between keratinocytes. By their long processes, they are able to transport melanin into cells by phagocytosis.

Knowing all this information about the structure, features of the upper layer of the skin, one can imagine what the epidermis is, how it looks and what is needed.