The skin, according to many dermatologists, is the most complex human organ. The presence of many layers and various functions, an abundant network of blood vessels and entire groups of nerve receptors provide it with the main place in protecting a person from environmental factors. Moreover, the skin also plays a communicative role, having the ability to receive from the outside world. And although the epidermis as the top layer is important only as a mechanical barrier, its value is very high.

General characteristics of the epidermis

The layer of dividing, maturing, dying and already dead cells is the epidermis. a whole tissue that has several layers, the cells of which originate from the same source, but are located at different levels depending on the degree of maturation. The epidermis is the first universal barrier that any environmental factor potentially dangerous to the body faces.

Layered structure: layers of skin

The structure of the skin is layered - 3 layers that perform different functions. The most important of these is the dermal, which has receptors and muscles. Hair is also located in the dermis. Moreover, their "ancestor", like nails, is the epidermis. the stratum corneum, located directly above the dermis and playing a protective role not only in relation to it, but to the whole organism. A little deeper than the dermis is a less important layer of the skin - fiber, where fat accumulates in adipocytes.

The layered structure of the epidermis

The deepest layer is the basal layer, which is entirely represented by cells capable of dividing. Due to them, damaged cells are restored and lost horny scales are replenished. In the thickness of the basal layer, there are single melanocytes that accumulate a black pigment substance (melanin), which is necessary for ultraviolet skin protection.

The spiny layer is located above the basal and is built in the form of 3-8 rows of living cells, already incapable of division. They are linked to each other by means of cytoplasmic outgrowths to give the skin mechanical strength. In areas of the skin exposed to frequent external influences, the number of layers of spiny cells increases to 8-10 pieces. In such places there are no sweat glands and hair: feet and palms. With frequent damage to other areas, the layers of the epidermis also thicken with the formation of calluses.

Immediately above the spiny layer is the granular layer, which is represented by half-dead epidermal cells. Their organelles lose their ability to generate energy, but accumulate a significant amount of tonofibrils. The granular layer consists of only 1-2 cell layers oriented parallel to the skin surface.

A shiny layer is a layer of cells completely devoid of organelles. Their purpose is mechanical protection of the skin and gradual death, degradation to the stratum corneum. The latter is superficial. This is a collection of dead squamous cells, which are an excellent barrier to pathogenic influences.

Functions of epidermal cells

The main function of the epidermis is the creation of mechanical, physical, biological and chemical barriers that delimit the internal environment of the body from potential and actually pathogenic factors. However, these are not all the roles played by the epidermis. What is it, and how is this explained?

Without melanocytes and keratinized cells, the functions of the epidermis would not be realized. play the role of a mechanical barrier, and melanocytes - an optical one. This means that the epidermis protects against damage and evaporation of the liquid, and pigment cells - from ultraviolet radiation. All this allowed a person to adapt to the conditions that are observed in the familiar world. After all, it was the development of the skin that allowed those organisms from which man originated to emerge from the water and conquer the land.

The main features of the epidermis

All layers of the skin have evolved phylogenetically to provide certain functions. The epidermis is designed to protect the dermis from mechanical, physical and chemical influences. It is needed to limit the loss of fluid, which can only evaporate from its surface after being secreted by the sweat glands. There is no other physiological way for fluid to leak from the body through the skin.

If we consider the epidermis from a cosmetic point of view, the following facts are obvious. This layer of skin cannot have wrinkles and scars, and there are no blood vessels in it. It is nourished by the diffusion of substances from the vessels of the dermis of the skin. Therefore its only cosmetic problems are the following: hyperkeratosis (thickened layers of the epidermis) and The fight against these phenomena, as well as psoriasis, requires treatment and the use of cosmetics.

Pathologies of the epidermis and melanocytes

There are several categories of diseases that the epidermis can suffer from. What is it and how these states manifest themselves, read below. The first category is diseases associated with increased reproduction of the epidermal cells of the basal layer. The disease is called psoriasis. There is also a congenital condition - ichthyosis, in which the baby is already born with hyperkeratosis and is not viable. The second group of diseases of the epidermis is tumor. Basalioma and melanoma can develop from the epidermis. The latter originates from melanocytes.

The epidermis is the actual epithelium, multi-layered keratinizing. The epidermis of the skin has five main layers (zones) that differ in their structure. The thickness of the epidermis is heterogeneous: in different places of the skin it is different. The thickest epidermis, with a pronounced keratinized layer, is located on the soles, a little thinner on the palms, and even thinner on the genitals and skin of the eyelids. Most epidermal cells produce keratin. These cells are called keratinocytes (spiky, basal, and granular). Melanocytes produce melanin, receptor cells contribute to the ability to touch. There are also special cells (Langerhans) in the epidermis that perform the function of protection against foreign bodies and microbes.

Layers of the epidermis

Basal layer- the closest layer of the epidermis. It consists of a prismatic single-row epithelium and a large number of slit-like spaces. The bulk of the cells here are keratinocytes containing chromatin and melanin. Between the basal keratinocytes are melanocytes containing great amount melanin. Melanin is formed in these cells from tyrosine in the presence of copper ions. This process is regulated by melanocyte-stimulating pituitary hormone, as well as catecholamines: adrenaline and norepinephrine; thyroxine, triiodothyronine and androgens. The synthesis of melatonin increases when the skin is exposed to ultraviolet radiation. Vitamin C plays a significant role in the synthesis of melanin. Among the cells of the basal epithelium there are few specific tactile cells (Merkel). They are larger than keratinocytes in size, contain osmiophilic granules. The basal layer provides attachment of the epidermis to the underlying skin and contains cambial epithelial elements.

Spiny layer. Above the basal layer is prickly (stratum spinosum). In this layer, keratinocytes are located in several layers. The cells of the spinous layer are large, their shape is irregular, gradually becoming flattened when approaching the granular layer. In addition, there are also desmosomes - specialized cell structures. Keratinocytes in the stratum spinosum contain very little chromatin, so they are paler. They have one feature: in their cytoplasm there are many special thin tonofibrils.

Granular layer(stratum granulosum) consists of spiny keratinocytes and process epidermocytes. It is assumed that these cells are "wandering" epidermal macrophages that perform protective function. In the granular layer, there are from 1 to 4 layers of flat cells, closely adjacent to each other. Their nuclei are poor in chromatin. A feature of the cells of the granular layer is the peculiar grains in their cytoplasm, consisting of a substance similar in structure to DNA. There are two main types of granules located in the cytoplasm of cells of the granular layer: keratoglian and lamellar. The former are necessary for the formation of keratin, while the latter provide moisture impermeability of the skin by releasing special lipid molecules on its surface.

glitter layer(stratum lucidum) is above the granular. This layer is quite thin, and is clearly visible only in those areas where the epidermis is most pronounced - on the skin of the palms and soles. Flat, homogeneous keratinocytes are the main cellular elements of this layer. The shiny layer is inherently transitional from living epithelial cells to keratinized scales located on the very surface of human skin.

stratum corneum(stratum corneum) - the layer of the epidermis that is in direct contact with the external environment. Its thickness varies in different parts of the skin, and very significantly. The most developed stratum corneum is on the palms and soles, much thinner on the abdomen, flexion surfaces of the arms and legs, sides, skin of the eyelids and genitals. The stratum corneum has in its composition only thin non-nuclear cells that are tightly adjacent to each other. Horny scales consist of keratin - a substance of an albuminoid nature, containing sulfur in excess, but little water. The scales of the stratum corneum are tightly connected to each other and provide a mechanical barrier to microorganisms.

The outer cover of the body has a rather complex structure. The 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 at the same time they forget about the second component of the skin - the dermis.

The structure of the outer cover of the body

The skin consists of two layers - the epidermis and the dermis. The upper epithelial layer is separated from the lower one by an uneven wavy line. Its appearance is due to the presence on the surface of the skin of special outgrowths - papillae. Its upper layer is keratinized squamous stratified epithelium. It does not have it, and it receives nutrition only from the dermis.

Having figured out what the epidermis is, finding out where it is located, many begin to be interested in its structure. It consists of cells of various shapes and structures. They reflect certain phases of their lives. The thickness of the epidermis, depending on 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 most (its upper layer) is in the pubic region, on the forearms, and the abdomen.

The structure of the upper keratinized cover

The epidermis consists of 5 distinct layers. Its main component is called keratinocyte. But the structure of the epidermis is more complicated than it might seem at first glance. Experts 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 cells of the epidermis are in a state of constant renewal. In the layers, the processes of reproduction, movement, keratinization and desquamation take place. Depending on the specific area of ​​the body, the process of complete renewal of the epidermis can take from 20 to 30 days.

stratum corneum

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

Due to this, these keratinized 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 may have loose or dense filling of keratin fibrils. On the surface are the second of them. And the first are located closer to the granular layer. In their structure, you can find the remnants of the cell organelles that were previously in them. These scales are often referred to as T-cells.

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

glitter layer

This part of the epidermis is not always expressed. It is also called the eleidine layer. If it can be detected, then it looks like a thin, light, bright and uniform strip. The layer got its name only due to its appearance. Its component is a substance called eleidin. It is a basis product for further keratinization of cells. It is found, as a rule, only in the skin of the soles and palms. It consists of non-nuclear flattened cells.

Granular layer

Those who have figured out what the epidermis is, figured 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 epidermis is thin. But it can also consist of 10 rows of cells in those places where the skin is denser. They are diamond-shaped, 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 keratohyalin. They are located so that the long axis of each diamond-shaped cell is parallel to the course of the groove or scallop.

Spiny cells

Regardless of the location of the skin area, the specified layer consists of 5-10 rows. The cells in it are in the form of polygons. When viewed under a microscope, one can see not only the layers of the epidermis of the skin, but also 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 prickly.

Keratinocytes are bound in this part of the epidermis by desmosomes. They have a rather complex structure: they look like 2 plates, and between them there are 4 electron-transparent and 3 electron-dense layers alternating with each other. It is desmosomes that support the internal structure of cells, they are the guarantor of a strong intercellular connection. They also serve as attachment sites for tonofilaments. It should be noted that the human epidermis is arranged in such a way that the number of desmosomes decreases in the upper parts of the spiny layer.

The cell structure resembles the components of the basal region. But at the same time, they are different. Spiny cells are interconnected by a significant number of desmosomes, and their bundles of tonofilaments are thicker.

Basal cells

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

Keranocytes in this layer look like cylinders that stand upright. They are distinguished by 2 types: with a flat and jagged surface. The first of them divide, due to them a change of cells occurs. The second perform a backup function. But with any damage to the skin, they begin to actively divide.

You can fully understand and understand how the structure of the epidermis is arranged if you know that the structure of the components of the basophilic layer is slightly different. In addition to both organelles and nuclei, which are common to all other cells, they contain specific structures - tonofilamens. Also there are special inclusions, which are called melanin granules.

Separately, it should be said that melanocytes are special cells that can produce melanin. This substance protects against destructive action. About 10-25% of these cells are located in the basal layer. In appearance, they resemble and are located between keratinocytes. Through their long processes, they are able to transport melanin into cells using 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 it is needed for.

To understand how cosmetic preparations and their individual components function, you need to have a good understanding of the basics. The main knowledge in cosmetology is the structure of the skin and its cells. In this article and in the next two, we will tell you about what the skin actually is, what functions are assigned to it, and find out the features of all its layers.

All this is necessary for those who want not just blindly to use cosmetics, but to understand the principle of its action. Despite the fact that this topic is very interesting, it can be called quite complex, and you can’t tell everything in one article. In this regard, we have divided our one topic into three sub-themes.

The first part will introduce you to the very concept of "skin", you will learn about its structure and main functions. We will talk about the epidermis in more detail - we will return the skin layer.

Skin: what is it

Since school lessons biology, we remember how puzzled we were by the information that a tomato is not quite a vegetable, and a watermelon is not a fruit, but, oddly enough, a real berry. So to find out that our skin is an organ is somehow unusual. But in the meantime, this is true. In addition, it is not just an organ, but it is considered the largest in the human body.

The skin has a mass, coupled with such a component as fiber, called subcutaneous fat, almost 17%, if we take our total mass as 100%. Since it is difficult to imagine, so let's give an example. Suppose a person weighs 60 kg, and of these, as many as 10 kg fall solely on the skin.

Another important point: The skin is the second organ in the body after the liver, which is capable of self-healing. There are no more such organs in our body. Renewal and revival of the skin after any kind of damage is its main feature.

What are the functions of the skin

The functions of the skin, it must be said, are many. We will tell you about the main ones:

* The skin is the protection of other organs from all kinds of mechanical damage.

* The skin helps to protect against the negative effects of ultraviolet radiation and high temperatures.

* Thanks to the skin, the risk of penetration of harmful bacteria and microbes into the body is reduced.

* It is through the skin that excess water, toxins and by-products of intensive metabolism are released.

* The skin is involved in the important process of regulating the temperature of our body, helping us not to overheat or overcool.

* Skin is an active participant in a vital process, namely water-salt metabolism.

In addition, the skin has close ties with the rest of the body and with each organ separately. It is the skin that will give us a signal in the event that some malfunctions begin inside. Here are some examples:

* Various skin inflammations, excessive greasiness can be symptoms of a hormonal disharmony that has arisen.

* Peeling and dryness, "snacks" (painful cracks) in the corners of the lips indicate beriberi.

* The feeling of itching and yellowness clearly signal problems with the liver.

* Bursting small blood vessels may well be due to the fact that not everything is good in the pancreas.

So do not ignore the "eloquent" signals of our skin, and they must be listened to.

What is leather made of?

The skin is a multi-layered organ. There are three of them. Now we will describe in detail the epidermis - our main defense.

Epidermis

So, this layer, as we have already understood, is the top one for our skin. In cosmetology, it is the epidermis that is the object of attention, because any cosmetics “works” with it. The deeper layers below the epidermis can only be reached by those drugs that are administered through injections.

Just the epidermis we call in ordinary life the skin. Its thickness is different in each of the sections: if we mean our soles, then this is about 2 mm, if we mean the eyelids, then in the region of 0.1 mm, and the average value of the thickness of the epidermis is 1 mm .

Structure

Although the epidermis is a layer of the skin, it is also multi-layered. There are exactly five of these levels. In addition to cells in these layers, there are many nerve receptors, there are hair channels, there are ducts of sweat and sebaceous glands.

It is worth noting that there are no blood vessels here, so it feeds and receives water directly from the dermis.

5 epidermal layers

So, let's list and analyze in order all 5 layers:

* The topmost is called horny. In it, from 15 to 20 rows are occupied by corneocides - these are non-living cells that do not have metabolism. There is only 10% of water in them, they are located very close. The cells are non-nuclear, but they contain keratin. Keratin is an insoluble solid protein, it is the main component that structures the upper layer of the epidermis. Due to the continuous contact of cells with intercellular fats, the integrity of the layer is maintained. It is when these bonds are weakened and then completely broken, and the process of exfoliation occurs. The upper epidermal layer is constantly in contact with the external environment. Its function is to determine the degree of penetration of various substances into the skin and protect it from negative impacts. The stratum corneum thickens with prolonged contact with the sun, friction or high temperatures, which allows us to talk about strengthening the protection of the skin.

* The next layer is called shiny. It has 2-4 cell rows, all cells are non-nuclear and flat. It must be said that this layer is not present on the entire body, but only in those places where the skin is thicker, that is, in the area of ​​\u200b\u200bthe palms and soles. It is needed to provide enhanced protection against the consequences that regular friction can lead to.

* The third layer is called granular. 1-4 rows of flattened small cells with transparent nuclei are located very close to each other. In this layer, the number of cellular organs (organelles) becomes smaller, but precursors of keratin appear. So called keratogeolin granules. The main function of the granular layer is to secrete intercellular fats to hold the cells of the upper stratum corneum of the epidermis and protect the skin from the penetration of unnecessary foreign substances and dehydration.

* The fourth layer is called prickly. There are already from 4 to 7 cell rows, all cells have nuclei. They also contain cellular organs, cytoplasm and water (70%). The layer got its name because of the presence of outgrowths resembling spikes in the cells. It is within this layer that the keratin mentioned above begins to be synthesized.

* The fifth layer is called basal. It is the last and lowest. Derama is directly on the border with it. The cells here are located in 1 row differ large sizes. They all have a cytoplasm and are nuclear and enveloped. There are also cellular organs, substances from the inorganic region and water of the order of 70%. It is at this level that cell reproduction occurs. After their inception, the cells begin to rise higher and higher until they reach the stratum corneum. It helps our skin to heal. And only in the layer called the basal, melanin is produced.

Three of the five layers - from granular to basal - are given the name of Malpigiev. They contain living cells with a membrane, nucleus and cytoplasm.

Types of epidermal cells

Now a few words about the varieties of cells of the epidermal layer. These include keratinocides, corneocides, melanocides.

Keratinocides are cells with more than 4 corners and small outgrowths. This type of cells is considered the most numerous among all other cells of the epidermis and the most important.

Keratinocides are the basis of all epidermal layers, and their life cycle is programmed. Keratinocides are formed in a layer called the basal layer and rise gradually to the stratum corneum. During this path, they lose water, organs, flatten and eventually die, turning into their continuation - into corneocytes.

It is from the corneocytes that the upper layer of the epidermis consists. 80% of them is keratin. From the moment of the birth of the cell until the moment of its death, 26-28 days pass, that is, almost a month. Exfoliation occurs due to the fact that the bonds between corneocytes are destroyed. The process of desquamation of corneocytes is called desquamation. If the desquamation process does not go as it should, then this can lead to the retention of cells in the skin and even the formation of malignant tumors.

Sometimes the keratinocide pathway can be disrupted. For example, cells in the basal layer divide more slowly than usual. This thins the epidermis, and the skin wears out and dulls. Or the cells do not exfoliate in time, which leads to a thickening of the upper layer. Both problems are solved with the help of appropriate medications.

As for melanocides, they are rather big cells with additional outgrowths. Melanocidyses are located in the basal layer, and outgrowths "pierce" the next two levels. Thanks to these cells, we get melanin, which is responsible for the desired skin color. Melanin is also a defense against harmful sun rays. The brighter the sun shines, the more melanin is produced.

In the epidermis, there are also cells responsible for immunity, cells responsible for how we feel with the skin, that is, for the tactile function, and cells called stem cells. They have the ability to degenerate into tissues of various types.

Summing up, we can say the following. Today we managed to find out that:

* The skin is the human organ itself big size and performs a variety of but important functions.

* The epidermal layer is the outer, that is, the upper one, and is also divided into several layers, namely five.

* The basal layer is the place where all epidermal cells are born.

* After the nucleated cells begin to rise up and, moving "from step to step", gradually lose their viability and turn into keratinized.

* The first layer of the epidermis is called the stratum corneum. Here, all relationships between cells are finally broken and they begin to exfoliate. This is a natural skin renewal process.

Knowing how the top layer of the skin is arranged, you can easily understand how cosmetic preparations work. After all, it is precisely on the epidermis that almost all of them are directed. Only with the help of injections can the means penetrate deeper.

Therefore, using all sorts of modern cosmetic inventions, you influence your appearance help our skin cells to regenerate and recover faster. And do not forget that thanks to the existence of keratinocide, we have such wonderful and useful procedures as peeling, as well as skin rejuvenation and nutrition systems.

Leather- this is the outer cover of the body, it is an organ with a very complex structure that performs a number of important vital functions. In addition to protecting the body from harmful external influences, the skin performs receptor, secretory, metabolic functions, plays a significant role in thermoregulation, etc.

The area of ​​the skin of an adult reaches an average of 1.6 m 2. The color of the skin depends on the translucence of the blood and the greater or lesser presence of melanin pigment. In the area of ​​\u200b\u200bnatural openings (mouth, nose, anus, urethra,) the skin passes into the mucous membrane. On the surface of the skin, one can find a peculiar pattern of triangular and rhombic fields, limited by grooves; it is especially distinct on the palms, fingers and soles. Almost all over the skin is covered with hair.

Rice. 1. The structure of the skin of a human finger: 1-5 - epidermis (1 - basal layer; 2 - spiny layer; 3 - granular layer; 4 - shiny layer; 5 - stratum corneum); 6 - excretory duct of the sweat gland; 7 and 8 - dermis (7 - papillary layer; 8 - reticular layer); 9 - terminal section of the sweat gland; 10 - adipose tissue.

Skin structure. Two sections are distinguished in the skin: the upper one is epithelial (epidermis) and the lower one is connective tissue (the skin itself is the dermis). The boundary between the epidermis and the dermis appears as an uneven wavy line due to the presence of special outgrowths on the surface of the dermis, the so-called dermal papillae (Fig. 1).

Epidermis consists of five layers of cells. The layer of the epidermis located directly on the border with the dermis is called the main basal layer. It consists of a single row of cells separated by narrow slit-like tubules and interconnected by protoplasmic processes. The cells of the basal layer have two features: 1) they constantly multiply and by differentiation form cells of the overlying layers; 2) melanin pigment is formed in these cells, and also contains.

The second layer is called the subulate. It consists of several rows of irregularly shaped cells with a light nucleus, also separated by slit-like tubules. The third layer is called granular: it consists of one or two rows of elongated, elongated cells, closely adjacent to each other.

In their protoplasm there are grains of keratohyalin, which is the first stage in the formation of horny substance. The fourth layer is called brilliant. It is found only in areas with a thick epidermis (palms, soles), has the appearance of a shiny strip, consisting of flattened non-nuclear cells, and is the next step in the formation of the horny substance. The last, upper, layer is the stratum corneum, consisting of thin nuclear-free cells, closely interconnected and containing a special protein substance - keratin. In the outermost part, the stratum corneum is less compact, individual plates lag behind each other, causing a constant physiological discharge of obsolete epithelial elements. The thickness of the epidermis and, in particular, its stratum corneum varies in different parts of the skin. It is most powerful on the palms and soles, much thinner on the lateral surfaces of the body, especially thin on the eyelids and external genitalia of men.

Dermis- connective tissue part of the skin, consisting of two layers: subepithelial, the so-called papillary, and mesh. The papillary layer is built from soft fibrous, consisting of thin bundles of collagen, elastic and argyrophilic (reticulin) fibers. The latter, on the border with the epithelium, together with the interstitial substance, form the so-called basement membrane, which plays an important role in the metabolic processes between the epithelium and the dermis. Collagen fibers of the papillary layer gradually pass into thicker bundles of the reticular layer and form here a dense plexus with large quantity elastic fibres. The reticular and papillary layers contain various cellular elements (fibroblasts, histiocytes, mast cells, etc.); among the connective tissue fibers are small bundles of smooth muscles associated with hair follicles.

Thick bundles of collagen fibers of the reticular layer pass directly into the subcutaneous adipose tissue, where they form a wide network, the loops of which are filled with fat cells. Adipose tissue determines the movable attachment of the skin to the underlying tissues and protects it from mechanical damage and ruptures.

The skin has a large number of blood and lymphatic vessels.

Arterial vessels form two networks. The first of them is located on the border between the dermis and subcutaneous tissue, smaller vessels depart from it into the reticular layer of the dermis. At the border with the papillary layer, they branch out and form a second network, from which capillaries extend, penetrating into the papillae (capillary loops). Venous vessels form three networks. One of them is located under the papillae, the second - in the lower half of the dermis and the third - in the subcutaneous adipose tissue. The epidermis is deprived