Sequence of skin layers. Skin care

What is leather? This is a natural barrier that is located between the external and human skin, which performs a number of very important functions and tasks and ensures the smooth functioning of the entire human body. In this article we will learn the importance of human skin, why it is needed, and what diseases it can be exposed to.

Skin functions

• Thermoregulation- this is a very important process that must regulate the human body temperature and maintain it constant, regardless of environmental conditions. More than 80% of heat exchange occurs through the skin.
• Receptor. Receptors are organs or cells that are capable of translating external influences into nerve impulses and transmitting signals from this influence to our nervous system. Pain and tactile receptors are located here. Those that react to cold and heat. On 1 square centimeter there are about 6 million cells, and of these there will be 5 thousand receptors that are responsible for the perception of certain external signals.
• Protective- a very important function, since it is the human skin, the significance of which is revealed in the article, that is a kind of barrier to the penetration of various infections through the surface of the body. Therefore, if there are any damage to the skin, they must be treated to prevent harmful substances from entering the human body. In addition, sweat is released onto the surface of the skin, which is acidic and kills most bacteria.
• Respiratory. Thanks to the skin, gas exchange occurs in the human body. Scientists are still arguing about the importance of gas exchange for human skin. But it is known for sure that we receive a large amount of oxygen through the skin.

• excretory. Together with sweat, all those components that need to be removed from the body for its proper functioning are released through the skin.
• Exchange. Regulation of water-salt and temperature balance. All this happens due to the exchange of substances with the environment. As a result, many processes occurring in the human body are regulated.
• Synthetic. The essence of this function is that a special pigment, melanin, is synthesized in human skin, which allows it to neutralize the effects of ultraviolet radiation. Melanin is a good antioxidant. In addition, with its help, the human body receives vitamin D, which protects it from bacterial infections and is still considered one of the best means of combating diseases such as tuberculosis. This vitamin causes the formation of protective peptides in the body, which activate the immune system, and destroys Koch's bacillus.
• Depositing blood. About 1 liter of blood can be retained in the blood vessels of the skin, which is especially necessary when wounds occur.
• Self-cleaning. The skin constantly loses its cells due to contact with the environment, but thanks to regeneration we hardly notice it.

All these functions perfectly show how important human skin is.

Skin structure

When answering the question of what leather is, it is necessary to dwell in more detail on the fact that it consists of three layers. The outer layer is called the epidermis. It is he who is constantly in contact with the environment. The second layer is the skin itself, or dermis, or also called dermis. And the deepest layer is subcutaneous fatty tissue, which in some people can reach a thickness of several centimeters. Let's look at all these three layers in more detail.

Epidermis

Dermis

The dermis is made up of connective tissue. Its main components are collagen and elastic fibers. They are what give the skin elasticity. Thanks to this property, we can move our limbs painlessly, while stretching the skin. In addition, the dermis contains receptors through which we feel touch, pain, cold and heat. Here are located sweat and sebaceous substances that release substances from the human body into the environment. Finally, the dermis contains the hair follicles and a small number of muscles that affect them.

Let's take a closer look at the glands and follicles. The glands are divided into sebaceous and sweat glands. The sebaceous glands secrete a special secretion called sebum, which prevents the penetration of water into the human body, as well as the loss of moisture from the body. A person will secrete about 20 g of sebaceous secretion during the day. Sweat glands look like twisted tubes with an excretory duct. Depending on the body type and intensity of physical activity, a person may produce about half a liter of sweat every day. Sweat plays a vital role in water-salt balance, controlling homeostasis as the constancy of the internal environment, and in the thermoregulation of the human body, since it cools it by evaporating from the surface of the body.

Hair follicles are located deep in the dermis and are the basis for hair growth. They are connected by blood vessels that bring oxygen and essential nutrients, and nerves.

Subcutaneous fat

This is the deepest layer, consisting mainly of adipose tissue and fat cells. This fat performs a number of beneficial functions. Firstly, it is a place where energy and fat-soluble vitamins are stored, thanks to which the human body can go without food for some time. Secondly, adipose tissue is an excellent thermal insulation material that protects the body from hypothermia. Thirdly, this layer of skin to a certain extent protects a person from injuries and fractures.

We answered in detail the question of what leather is. Now let's turn to diseases that the skin can be exposed to, as well as methods of treatment.

Skin diseases and treatment

What is leather? It is first and foremost an organ. And therefore, like any other human organ, it can get sick. What are the main problems associated with human skin?

Hives

Blisters on the skin, redness, itching - almost every one of us has encountered such problems at least once in our lives, and some suffer from this constantly. Urticaria, as this disease is called, can be caused by many reasons. This includes poor nutrition, contact with synthetic materials, and, of course, allergies. Hives are easy to differentiate from other skin problems. It is characterized by blisters and itching. In addition, urticaria goes away quite quickly (if we are not talking about a chronic disease). Blisters stay on the skin for no more than a day. For urticaria, various antihistamines are usually prescribed.

Fungal diseases. Rubromycosis

Despite great preventive medical work, fungal diseases are still widespread. Rubromycosis is the most common. It affects the skin of the feet and interdigital folds. With this disease, floury peeling and cracks appear. In the absence of timely treatment, the disease from the feet can spread further over the entire surface of the skin. For rubromycosis, antifungal ointments and keratolytic drugs are prescribed.

Athlete's foot

The most common form of the disease is interdigital. Cracks, loosening, and weeping erosions appear. Most often, athletes and workers in hot shops suffer from this disease. If you consult a doctor in a timely manner, the disease can be easily cured with conventional antifungal drugs.

Microsporia

Another disease of the scalp, which very often affects children. The fact is that animals are carriers of this disease. Round lesions with clear contours appear on the skin. Pustules and peeling may appear. When the disease spreads to the scalp, hair may break off 4-6 mm from the surface of the skin. If such foci of disease are detected, you should consult a doctor. As a rule, a dermatologist prescribes antifungal ointments, and in case of advanced disease, products that contain a hormonal component.

The skin, photos of all its components are presented in the article, suffers from many influences and diseases. We have listed only the most basic of them.

The skin, with its surface area of ​​1.5-2 square meters, is the largest organ of the human body. It performs numerous functions. The condition of the skin depends on age, nutrition and lifestyle. This is especially true for facial skin, because it is more strongly affected by all the harmful effects of the environment. In addition, the face is the most exposed part of the skin and requires careful care.

Our skin is:
about 5 million hairs; - the total surface area of ​​the skin is 1.5-2 square meters;
contains 60% moisture, in children up to 90%;
one hundred pores per square centimeter;
two hundred receptors per square centimeter;
average skin thickness 1-2 mm;
the skin is slightly rougher and thicker on the soles, thinner and more transparent on the eyelids;
the weight of the skin without the hypodermis is 4-6% of the total body weight;
on average, 18 kg of dead and newly replaced skin over the lifetime of an adult.

The skin has a very complex structure; it is penetrated by a huge number of vessels, nerves, ducts of the sebaceous and sweat glands.

Very simply, the structure of the skin can be described as follows:
1. The outer layer of the skin is the epidermis, formed by epithelial cells lying on top of each other in several dozen layers. The upper part of the epidermis, which has direct contact with the external environment, is the stratum corneum. It consists of aged and keratinized cells that are constantly exfoliated from the surface of the skin and replaced by young ones migrating from the deep layers of the epidermis. (Complete renewal of the epidermis, for example, on the sole lasts about a month, and on the elbow - 10 days).
We owe it to the stratum corneum that our body does not dry out and foreign substances and pathogens do not penetrate inside. Significant assistance in this is provided by the so-called protective acid mantle (also called hydro-lipid mantle), which covers the surface of the skin with a thin film. It consists of the fat of the sebaceous glands, sweat and components of viscous substances that bind individual horn cells. The protective acid mantle can be considered as the skin's own cream. It is slightly acidic (compared to an alkaline environment, which is why it is called acidic) - a chemical environment in which bacteria and fungi usually die.
In the deepest layer of the epidermis there are melanocytes - cells that produce the pigment melanin. The color of the skin depends on the amount of this pigment - the more of it, the darker it is. The formation of melanin is enhanced by ultraviolet rays, which is the cause of tanning.
2. The next layer, the dermis, is also heterogeneous. In its upper part, located directly under the epidermis, there are sebaceous glands. Their secretions, together with the secretion of the sweat glands, form a thin film on the surface of the skin - a water-fat mantle, which protects the skin from harmful influences and microorganisms. The underlying elastic fibers give the skin its elasticity, and the collagen fibers give it strength.
3. And finally, the third layer of skin - the hypodermis (or subcutaneous tissue) - serves as a heat-insulating lining and softens the mechanical effects on the internal organs.

The skin itself consists of two layers - papillary and reticular. It contains collagen, elastic and reticular fibers that make up the skin framework.

In the papillary layer the fibers are softer and thinner; in the mesh they form denser bundles. The skin feels dense and elastic to the touch. These qualities depend on the presence of elastic fibers in the skin. The reticular layer of the skin contains sweat, sebaceous glands and hair. Subcutaneous fatty tissue in different parts of the body has unequal thickness: on the stomach, buttocks, and palms it is well developed; on the auricles and the red border of the lips it is very weakly expressed. In obese people, the skin is inactive; in thin and emaciated people, it easily shifts. Fat reserves are deposited in the subcutaneous tissue, which are used up during illness or other unfavorable cases. Subcutaneous tissue protects the body from bruises and hypothermia. In the skin itself and subcutaneous tissue there are blood and lymphatic vessels, nerve endings, hair follicles, sweat and sebaceous glands, and muscles.

How the skin breathes and what it nourishes

Exactly a quarter of all blood circulates in the skin, supplying it with everything necessary for the formation of young cells and to support active ones: oxygen for “breathing” of the skin (more precisely, as fuel for metabolism in the skin), energy-supplying carbohydrates (for example, glycogen), peptides and amino acids for the formation of protein, fats (also called lipids), vitamins and microelements.

Arterial vessels in the skin form superficial and deep networks. The first is located at the level of the base of the skin papillae; the second is at the border of the skin itself and subcutaneous tissue. The superficial arterial network connects to the deep one. The distribution of blood vessels is of great importance for the color of the skin. The closer the vascular network is to the surface of the skin, the brighter the blush.

Epidermal cells are nourished by lymph penetrating from the skin itself. The skin contains a large number of nerve endings. Nerves also form two networks in the skin, running parallel to the vascular ones; in the epidermis they end in nerve fibers and free endings. The sensitivity of the skin is very high, since, in addition to nerves, special nerve apparatuses are also located in the subcutaneous fatty tissue. They convey sensations of pressure, touch, cold and heat. Nerves and nervous apparatus of the skin connect it with all internal organs and the brain.

In principle, the skin can do without external nutrition. However, there is one subtlety here - at least in relation to the outer skin. Since the epidermis, unlike the lower layers, does not have its own blood vessels, it must receive its nutrition from capillaries in the mamillary boundary layer of the dermis. The close, serrated connection of both layers of skin, which guarantees good supply, becomes increasingly flat and weak over the years. This can lead to insufficient oxygen and nutrients reaching the upper skin. Compensating for this deficiency is one of the most important tasks of cosmetics.

How skin renews itself

The germinal layer is especially important because it is here that young cells are constantly being produced. Over the course of 28 days, they move to the surface of the skin, losing their cell nucleus. And with flat, “dead” keratin peels, they finally form the visible surface layer of the skin, the so-called stratum corneum. Dead cells fall off during daily friction when washing, wiping, etc. (two billion every day!) and are constantly replaced from below by others. This process is called regeneration. Within three to four weeks, the entire outer skin is completely renewed. If this cycle operates smoothly and without interference, the upper skin perfectly protects the lower layers - the dermis and subcutaneous layer. On top of the dermis is a layer of outer skin, which in turn is divided into five different layers. At the very bottom, the germinal layer forms young keratin, pigment and immune cells. Over the course of 28 days, they move upward and become increasingly flatter. And finally, in the form of dry peels without a core, they form a protective stratum corneum approximately 0.03 mm thick.

The peeling process underlies many cosmetic procedures that promote increased rejection of the most superficial stratum corneum of the epidermis, for example, when removing freckles, age spots, etc.

The skin contains nerve endings and nervous apparatus that sense temperature stimulation. Cold is perceived faster than heat. However, both cold and heat are felt differently on different parts of the body. The skin of the face is the least sensitive to cold and heat; the skin of the extremities is the most sensitive. The sensitivity of the skin to temperature irritations is evidenced by the fact that the skin senses a difference in temperature of 0.5 °C.

We owe it to the skin that the body temperature of a healthy person remains constant at about 37 degrees - regardless of the ambient temperature. It regulates the exchange of heat between the body and the external environment. Thermoregulation depends on the nervous system. Irritation of the nerves causes blood vessels to dilate or constrict; When contracting, heat is retained in the body; when expanding, greater heat transfer occurs.

However, this “vascular gymnastics” can lead to the appearance of red veins on the face, namely when the skin is delicate and the connective tissues are too weak to support the thin walls of the blood vessels from the outside. The vessels remain dilated and are visible through the skin.

Sweat glands play a significant role in heat transfer. The average person produces 600 to 900 ml of sweat per day. Evaporation from the surface of the skin causes a decrease in body temperature. When the external temperature decreases, heat transfer decreases, and when it increases, it increases.

Although cosmetics is mainly concerned with the skin of the face, it is important to know the function of the skin as an organ for the health of the body as a whole. Moreover, the skin of the face is always affected by a violation of its functions.

The skin is closely connected with all organs and systems of the body. It performs a number of diverse functions related to metabolism. It removes toxins and participates in water-salt, carbohydrate and protein metabolism. Its great importance in the functioning of the immune system has been proven.

Skin is the fifth sense organ

Together with the eyes, ears, mouth and nose, the skin belongs to the five sense organs. It is not only the largest, but also the most sensitive organ among them. She notifies us with lightning speed about hot, prickly and spicy things. The skin owes its incredible sensitivity to tiny tactile bodies, pressure, cold and heat receptors, free nerve fibers and other sensors in the connective tissue and dermis. They are directly connected through nerve pathways to the brain and spinal cord. There, the delivered information is quickly evaluated, converted into sensations, and, if necessary, into actions.

Leather - chemical laboratory

When exposed to sunlight, the skin synthesizes vitamin D. It is responsible for ensuring that the body has enough calcium for bone formation, as well as for many other metabolic processes.
under the influence of irritation by light, other special cells convert amino acids until the coloring substance melanin appears. This pigment acts as a “natural umbrella” to protect the skin from ultraviolet radiation and its destructive effects on cells.
A further skill of the skin is the ability of some of its enzymes to activate suitable hormones. For example, cortisone in the skin is converted into an even more effective substance hydrocortisone, and the male sex hormone testosterone is converted into dihydrotestosterone. In this form, it sensitizes the hair roots and sebaceous glands and can cause hair loss, oily skin and the formation of acne (a disease called acne).

Cleotheca

– a type of skin caused by excessive activity of the sebaceous glands and characterized by a rough texture, unhealthy color and shine. Those with oily skin face enlarged pores, comedones, sebaceous gland cysts, acne, and manifestations of seborrhea. Oily skin requires increased attention to existing problems, a certain diet, proper home and professional care (cleansing, masks, peelings, mesotherapy), and competent selection of cosmetics. To find out the causes of oily skin, consultations with a cosmetologist, dermatologist, and endocrinologist are necessary.

General information

Oily skin is one of the types of problem skin, characterized by increased greasiness and a shiny appearance. Depending on the secretory activity of the sebaceous glands, in cosmetology and dermatology it is customary to distinguish 4 types of skin: normal, dry, oily, combination (mixed). It should be noted that each skin type in itself is a variant of the norm and cannot be considered a disease. At the same time, different types of skin have their own characteristics, advantages and disadvantages, and therefore require a differentiated approach. Typically, skin type changes with age; In addition, the constant use of various cosmetics and makeup can create a false impression of the true characteristics of the skin. Oily facial skin is one of the most common types and is more prone to various dermatological problems than others. That is why oily skin needs special daily hygienic and competent professional care.

Causes of oily skin

Most often, oily skin occurs in adolescence and young adulthood and by the age of 25-30 it turns into another type (usually combination). Only 5-8% of people remain with oily skin throughout their lives. The direct cause of increased oily skin is the increased work of the sebaceous glands, which in turn can be caused by hereditary characteristics, hormonal imbalance, gastrointestinal disorders, poor nutrition, and improper skin care.

The presence of oily skin can be genetically determined - in this case, skin type does not change with age. In such a situation, the main efforts should be aimed at ensuring proper daily care and rational selection of cosmetics. Endocrine causes are associated primarily with puberty, during which the amount of testosterone increases, which increases the size of the sebaceous glands and increases the production of sebum. Other hormones also influence the function of the sebaceous glands, for example, adrenaline, the level of which in the blood increases in people experiencing stress. In women, increased oily skin may occur with prolonged or uncontrolled use of hormonal contraceptives, polycystic ovary syndrome, and less commonly during pregnancy or menopause. Oily facial skin combined with general dry skin is characteristic of hypothyroidism.

Among the nutritional reasons that contribute to the appearance of oily skin, one should highlight the abuse of fatty or spicy foods, as well as flour products, sweets, fast food, carbonated drinks, and alcohol. Quite often, people with oily skin suffer from diseases of the gastrointestinal tract (cholecystitis, colitis, constipation, etc.). Long stays and work in polluted and dusty rooms have a negative impact on the condition of the skin.

A typical mistake of those with oily skin is overly active and aggressive cleansing of the skin using alcohol-containing cosmetics and scrubs. Regular degreasing of problem areas of the skin with tonics and lotions only leads to aggravation of the problem: in response to the removal of the surface lipid layer, the epidermis reacts by increasing the secretion of glandular secretions. Frequent mechanical cleansing and peeling of the face causes microtrauma to the epidermis and intense sebum production. Using inappropriate creams and skin care products can also increase the problem of oily skin.

Characteristics of oily skin

Most often, oily skin is localized in the so-called T-zone, which includes the forehead, nose and chin. Externally, oily skin appears shiny, oily, unkempt, thick, and rough, and often has an uneven surface, dull color, and a grayish tint. Makeup does not apply well to oily skin; Foundations and powders remove oily shine only temporarily. Areas of problem skin are also found on the body, usually in the chest and back; Oily skin of the face and body is often combined with oily hair.

Insufficient cleansing of the skin from excess sebum leads to the fact that the sebaceous secretion, along with dead skin flakes and dust, clogs the pores and contributes to their funnel-shaped expansion. Often, oily, porous skin looks like an orange peel. In addition to excessive shine and enlarged pores, oily skin is prone to the formation of comedones (black plugs in the openings of the sebaceous glands) and milia (whiteheads), and acne. Spider veins (telangiectasia) are more often visible on it. If, against the background of increased sebum production, its qualitative composition also changes, a pathological condition such as seborrhea occurs.

Despite all the disadvantages of oily skin, it also has certain advantages. Thus, it retains moisture better, and, therefore, is more protected and less sensitive to the effects of various adverse atmospheric factors (wind, sunlight, low temperatures). Thanks to this, this type of skin is less susceptible to photoaging, retains its elasticity longer, and age-related wrinkles in those with oily skin appear later than in women with other skin types.

If inflammation persists on oily skin for a long time, you should consult a dermatologist to rule out demodicosis. To find out the causes of increased oily skin, consultation and examination of a dermatologist, gastroenterologist, endocrinologist, or gynecologist-endocrinologist may be required.

Features of oily skin care

The main tasks of caring for oily skin are removing excess sebum, opening pores, and reducing the activity of the sebaceous glands. First of all, it is necessary to minimize or completely eliminate the negative impact on the skin (refuse to use alcohol-containing lotions, fatty creams, frequent skin scrubbing, etc.). It is strictly unacceptable to leave decorative cosmetics on the skin overnight. The basis of the diet of the owner of oily skin should be lean meats, fish, vegetables, fruits, bran, cereals; Spices, smoked meats, baked goods and baked goods, and sweets should be limited as much as possible. Food should be rich in vitamins, especially group B.

It is advisable to divide the actual care for oily skin into home and professional care. Daily self-care for oily skin involves cleansing, moisturizing and nourishing procedures. First of all, you need to wash your face twice a day using a special foam, gel and mousse for oily skin. As a rule, such products have an anti-inflammatory and sebum-regulating effect, but do not dry out the skin. When washing, you should not use a washcloth or sponge, or hot water, as these products will further stimulate the secretion of sebum. It is preferable to lather the skin with a cotton pad or fingertips, and rinse off the cleanser with warm or cool water. Traditional medicine recommends for oily skin washing and steam baths with herbal decoctions (chamomile, linden blossom, horsetail, mint, nettle) while taking these infusions orally.

More thorough cleansing of oily skin through cosmetic peeling can be done once or maximum twice a week. In addition to the scrub, you can use peeling-gommage to deep cleanse the skin: such film masks effectively remove dead horn cells, dust particles and excess sebum without damaging the skin. Once a week it is useful to make clay masks that have an adsorbing effect, or fruit masks that have the effect of tightening pores.

After washing your face, you need to blot it with a soft towel or napkin and wipe it with a tonic for oily skin - such products contain disinfecting, sebum-regulating and pore-tightening components. The finishing touch to daily care for oily skin is the application of a cream designed for this skin type. Typically, creams, emulsions or hydrogels for oily skin have a liquid consistency and are quickly absorbed without leaving a shiny shine.

When choosing decorative cosmetics for daytime makeup, you need to pay attention to the quality, composition of the product and recommendations for use from the manufacturers. For oily skin, it is better to choose light foundations, foundations and powders with a mattifying effect that eliminate excess shine. You should avoid using cream blush, eye shadow, and liquid eyeliner - otherwise, cosmetics may “float” on your face within a couple of hours after application.

To understand how cosmetic products and their individual components work, 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 we will find out the features of all its layers.

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

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

Leather: what is it?

Even from school biology lessons, we remember how puzzled we were by the information that a tomato is not exactly a vegetable, and a watermelon is not a fruit, but, oddly enough, a real berry. It’s somehow unusual to find out that our skin is an organ. But meanwhile this is really so. Moreover, this is not just an organ, but it is considered the largest in the human body.

The skin has a mass, together with such a component as fiber, called subcutaneous fat, almost 17%, if we take our total mass as 100%. Since this is difficult to imagine, let's give an example. Let's say a person weighs 60 kg, and of this, as much as 10 kg is exclusively 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 other such organs in our body. Renewal and revival of the skin after any kind of damage is its main feature.

What functions does skin have?

It must be said that the skin has a lot of functions. We will tell you about the main ones:

* The skin protects other organs from all kinds of mechanical damage.

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

* Thanks to the skin, the risk of harmful bacteria and germs entering the body is reduced.

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

* The skin is involved in the important process of regulating our body temperature, 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 connections with the rest of the body and with each organ separately. It is the skin that will give us a signal if some kind of malfunction begins inside. Here are some examples:

* Various skin inflammations and excessive oiliness can be symptoms of hormonal disharmony.

* Peeling and dryness, “snacks” (painful cracks) in the corners of the lips indicate vitamin deficiency.

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

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

So you shouldn’t ignore the “eloquent” signals from our skin, but you definitely need to listen to them.

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 already understood, is the top layer for our skin. In cosmetology, it is the epidermis that is the object of attention, because this is what any cosmetic “works” with. Only those drugs that are administered through injections can reach the deeper layers below the epidermis.

It is the epidermis that we call skin in everyday life. Its thickness is different in each area: if we mean our soles, then it is about 2 mm, if we mean eyelids, then it is around 0.1 mm, and the average 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, these layers contain many nerve receptors, hair canals, and ducts of sweat and sebaceous glands.

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

5 epidermal layers

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

* The uppermost one is called the horny one. In it, from 15 to 20 rows are occupied by corneocids - these are non-living cells that do not have metabolism. There is only 10% water in them, they are located very close. The cells are nuclear-free, 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 connections are weakened and then completely broken that 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 influences. The stratum corneum thickens with prolonged contact with the sun, friction or high temperatures, which suggests increased skin protection.

*The next layer is called shiny. It has 2-4 cell rows, all cells are anucleate 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 ​​​​the palms and soles. It is needed to provide enhanced protection against the consequences that regular friction can cause.

* The third layer is called granular. 1-4 rows of flattened small cells with transparent nuclei, located very close to each other. In this layer, the number of cellular organs (organoids) becomes smaller, but precursors of keratin appear. This is what keratogeolin granules are called. The main function of the granular layer is to secrete intercellular fats to strengthen 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 spinous. 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 due to the presence of spine-like projections on the cells. It is within this layer that the keratin mentioned above begins to be synthesized.

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

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

Types of epidermal cells

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

Keratinocides are cells with more than 4 angles and small projections. This type of cell 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 gradually rise to the stratum corneum. During this path, they lose water, organs, become flattened and ultimately die, turning into their continuation - corneocytes.

It is the corneocytes that make up the upper layer of the epidermis. 80% of them are keratin. From the moment the cell is born until the moment it dies, 26-28 days pass, that is, almost a month. Peeling occurs due to the fact that the connections between corneocytes are destroyed. The process of corneocytes sloughing off is called desquamation. If the desquamation process does not proceed as it should, this can lead to cell retention 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 becomes dull. Or the cells do not exfoliate in time, which leads to a thickening of the top layer. Both problems can be solved with the help of appropriate medications.

As for melanocids, they are rather large cells with additional outgrowths. Melanocides are located in the basal layer, and the outgrowths “pierce” the next two levels. Thanks to these cells, we receive melanin, which is responsible for the desired skin color. Melanin also provides protection 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 our skin, that is, for the tactile function, and cells called stem cells. They have the ability to degenerate into different types of tissue.

To summarize, we can say the following. Today we managed to find out that:

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

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

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

* Afterwards, the nascent cells begin to rise up and, moving “from step to step,” gradually lose their viability and turn into keratinized cells.

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

Knowing how the top layer of skin works, you can easily understand how cosmetic products work. After all, almost all of them are aimed at the epidermis. Only with the help of injections can the agents penetrate deeper.

Therefore, using all kinds of modern cosmetic inventions, you influence your appearance, help our skin cells regenerate and recover faster. And don’t 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.

The skin is the soft outer shell. The skin protects the body from pathogens and external influences, excessive loss of water, takes part in respiration and thermoregulation, and metabolic processes.

The skin is the largest organ in area: in an adult, the skin area reaches 1.5-2 square meters.

The skin consists of the epidermis, the skin itself (dermis) and subcutaneous fat (hypodermis).

Epidermis- This is the outer layer of the skin, which is formed by stratified squamous epithelium. The surface layers of the epithelium become keratinized and gradually slough off. The thickness of the epidermis depends on the pressure experienced: on the chest, abdomen, neck, forearm the thickness of the epidermis is 0.1-0.5 mm, and on the sole and palmar surface of the hand its thickness is up to 2.3 mm.

The epidermis contains five layers of epidermal cells:

• basal layer - the lowest layer, located on the basement membrane
• stratum spinosum – located just above the stratum basale
• granular layer - the next one after the spinous layer
• shiny layer - visible on the palms and soles
• stratum corneum - consists of stratified keratinizing epithelium

In the deep layer of the epidermis, which is adjacent to the dermis (the skin's own), the reproduction and development of new cells constantly occurs. Thanks to this, the superficial, stratum corneum of the epidermis is renewed in 7-11 days. Skin color depends on the pigment melanin, which is located in the deep layer of the epidermis.

The skin itself (dermis) consists of fibrous connective tissue. Its thickness is 1-2.5 mm. The dermis contains papillary and reticular layers.

The papillary layer is located on the border with the epidermis. The papillae form ridges and grooves of the skin that protrude from its surface. The openings of the sweat glands open on the scallops. The interweaving of ridges and grooves creates an individual pattern on the palms and soles of each person that does not change throughout life.

The reticular, deeper layer of the dermis contains bundles of collagen, elastic and smooth muscle fibers, which determine the density and elasticity of the skin. The reticular layer of the dermis contains sweat and sebaceous glands, as well as hair roots.

Subcutaneous fat plays an important role in thermoregulation, protection of internal organs, accumulation and storage of nutrients. It consists of bundles of connective tissue and fatty deposits, which are penetrated by blood vessels and nerve fibers. The amount of fat deposits depends on gender (in women, in general, the subcutaneous layer is better expressed), the individual characteristics of the body, diet, lifestyle, physical activity, etc. The most fat deposits are in the chest, abdomen and pelvis. On the forehead and nose the fat layer is weakly expressed, and on the eyelids it is not at all. On the soles, palms and in the buttocks (places of greatest pressure), subcutaneous fatty tissue takes on the role of an elastic layer and has a cellular structure. Fat fiber conducts heat poorly, so well-fed people feel less cold than thin people.

Skin derivatives (hair and nails)

In addition to the skin, our body has its anatomical derivatives, which develop from the skin and its rudiments. Derivatives of the skin are hair and nails.

Hair are found on almost the entire surface of the body. Only the soles, palms, palmar and plantar surfaces of the fingers, the terminal phalanges of the fingers, the red border of the lips, the head of the penis, the inner layer of the foreskin, the labia minora and the clitoris are not covered with hair. There are long hair (on the head, pubic area and in the armpit area), bristly hair (eyelashes, eyebrows, ear and nostril hair) and vellus hair (on the rest of the body). The amount of hair depends on gender and age.

Hair has a shaft that protrudes above the surface of the skin and a root that lies deep within the skin. The hair root is surrounded by a hair follicle into which the sebaceous gland duct opens. A bundle of smooth muscle cells is attached to the hair follicle. Contraction of this bundle leads to straightening of the hair (“goose bumps”) and emptying of the sebaceous gland. Hair grows due to cell division in the lower part of the root (hair follicle) at a rate of approximately 0.2 mm per day. Hair color depends on the pigment and air content in the hair. With age, the pigment is destroyed and air accumulates - the hair turns grey.

Nails They are horny plates that lie on the nail bed, bounded at the base and sides by the nail folds. Nails grow at a rate of approximately 0.15 mm per day, changing on the fingers every 3 months, and on the toes every 4.5 months. On average, a person cuts about 4 meters of nails during his life.

Skin glands

Part of the outer covering of the body are various secretions of glands that are located in the skin. Skin glands include:

• Sebaceous glands, which secrete sebum to lubricate the hair and protect the skin. There are many sebaceous glands in the scalp, but there are none in the skin of the palms and soles.
• Sweat glands, which release water and dissolved metabolic products from the body. During the day, the sweat glands produce 0.5-0.6 liters of sweat under normal conditions and up to several liters in the heat or during physical work. Sweat consists of 98% water and 2% organic inorganic substances. The evaporation of sweat protects the body from overheating and promotes the excretion of salts, urea, uric acid, ammonia and other substances. The sex glands are most densely located in the area of ​​the palms, soles, axillary fossae, inguinal folds and on the forehead.
• Mammary gland– developed in women and secrete breast milk to feed the newborn baby.

Functions and types of skin

The skin performs the following functions:

• protective function – the skin protects the body from the effects of mechanical and chemical factors, microbes, water loss and water ingress from the outside;
• respiratory function - the skin is able to absorb oxygen and release carbon dioxide;
• thermoregulatory function - excess heat is studied and sweat evaporates;
• the skin participates in water-salt exchange during sweating;
• metabolic function - synthesis and accumulation of vitamin D and some hormones occurs in the skin;
• the receptor function is performed by the skin due to numerous nerve endings;
• immune function - the capture and transport of antigens is carried out with the development of an immune reaction.

Highlight fat skin on the palms and soles, which is formed by a thick epidermis (400-600 microns), without hair and sebaceous glands, and thin skin on the remaining parts of the body, consisting of a thin epidermis (70-140 microns), with hair and skin glands.

Skin receptors

The skin perceives tactile, pain and temperature irritations from the external environment. Sensitive nerve endings (receptors) are located in different layers of the skin and have different structures. The highest density of receptors is observed in the skin of the lips and on the pads of the fingers, and the lowest - on the back, shoulders and hips. On average, there are 170 receptors on 1 square centimeter of skin.

The following types of sensory nerve endings are distinguished:

• Mechanoreceptors- perceive touch, pressure and vibration. When analyzing irritations in the cerebral cortex, a subjective feeling arises about the object that the person touched.
• Thermoreceptors:
  • cold receptors - there are more of them than thermal ones, they are located closer to the epidermis;
  • thermal receptors are located in the deep layers of the dermis and subcutaneous tissue.
• Nocireceptors perceive pain sensations. The number of pain receptors is much greater than the number of tactile and temperature ones. Painful sensations occur when exposed to any strong irritant; they signal danger and cause defensive reflexes. The skin of the fingers is the most sensitive.