Respiratory function of the skin. The metabolic function of the skin

Plastic surgeon Levitskaya Maria Grigorievna and dermatologist-cosmetologist Chaikina Svetlana Anatolyevna tell:

D I think if I tell you that human skin is the largest organ of our body in terms of area, no one will be surprised. Everyone knows that the average area of the skin of an adult is about 2 m 2, and its weight is about 15% of body weight. But the fact that the skin plays an important role in the life of the body, hardly anyone thinks.

TO The skin is a natural protective barrier, an insulating sheath, thanks to which, in principle, the existence of a person is possible. It is a unique organ, just like the liver, kidneys or lungs. At the same time, the skin is a unique system that performs many different functions. Human skin is constantly exposed to the environment. Appearance, the condition and quality of the skin primarily depends on genetics and age, but we must not forget that it, like a mirror, reflects on its surface all our internal diseases, lifestyle, diet and even emotions.

B ice or redness increased sweating and active facial expressions leave their traces on it. To properly care for and keep the skin healthy and attractive, it is important to know its structure and understand the basic principles of work.

SKIN FUNCTIONS:

1. Protective function

TO Ozha performs a barrier role in maintaining the balance of the internal environment and protects the human body from the influence of the environment, mechanical, thermal and other external influences. High density, elasticity, good ability to regeneration (recovery), strength, as well as cushioning properties of subcutaneous adipose tissue help it fight infection, the consequences of bruises, sprains, etc. A dense stratum corneum and protective pigmentation (tanning) reduce harm from solar radiation.

2. Thermoregulation function

The processes of heat exchange with the environment, the preservation and release of excess heat are important for our normal existence.

Body temperature in different areas differs significantly: lower skin temperature is noted on the hands and feet, higher (36-37 ° C) - in the armpit, where it is usually determined.

As a rule, during the day there are small fluctuations (ups and downs) in body temperature in accordance with the daily biorhythm: the maximum is observed in the evening at 16-19 o'clock, and the minimum temperature is observed at 2-4 o'clock in the morning.

The process of removing heat from the body through the surface of the skin is called physical thermoregulation, which is carried out with the help of radiation (radiation), convection (evaporation), conduction (heat conduction) and evaporation. In a state of relative rest, an adult releases 15% of heat into the external environment through heat conduction, about 66% through heat radiation and 19% through water evaporation.

Conduction is the direct transfer of heat to objects or particles of the environment adjacent to the skin. This process is the more intense, the greater the temperature difference between the surface of the body and the surrounding air. Heat transfer increases with the movement of air (wind), while heat transfer in water occurs faster than in air. Clothing reduces or even stops heat conduction.

TO As mentioned above, most of the heat is removed from the body using infrared radiation (radiation).

The regulation of heat exchange is carried out reflexively, by changing the lumen of the skin vessels penetrating the entire skin. An increase in ambient temperature causes the areolas and capillaries to expand, which increases heat transfer, and the skin becomes warm and red. When the ambient temperature drops, the vessels narrow, while the outflow of blood to the internal organs occurs and the body's heat loss decreases, the skin becomes pale and cold.

An equally effective element of thermoregulation of the skin is evaporation from the surface of the body of water - 2/3 of moisture is removed with sweating, and only 1/3 with breathing. Evaporation of fluid excreted by the skin in the form of sweat leads to cooling of its surface and the whole body.

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1. For humans, an increase in body temperature above 43°C and a decrease below 25°C is usually fatal. Nerve cells are especially sensitive to changes in temperature.

2. In children of the first year of life, imperfection of thermoregulation is observed, which is associated with larger area skin surface per kilogram of weight, small thickness of the skin and its low thermal insulation capacity, as well as a very dense network of skin vessels, which contribute to more active heat transfer. In addition, young children practically do not sweat, and muscle tremors low temperatures they do not occur at all. Thermoregulation is carried out only by accelerating or slowing down the overall metabolism and the production of internal heat. Such a weak heat exchange system leads to the fact that small children can easily freeze in a relatively warm room, and when the ambient temperature drops below 15 ° C, hypothermia occurs. child's body. Also, children quickly overheat at the slightest increase in ambient temperature. As experience shows, most often children overheat, and freeze much less often.

The maturation of the mechanisms of thermoregulation occurs gradually: by 6-12 months, the regulation of heat transfer through the reactions of superficial vessels begins to work well, and the formation of heat transfer is completed only by the age of 7-8, while the sweating process is adequately adjusted at an even later age.

3. The parts of the body through which the primary exchange of heat with the environment occurs are called heat exchangers. In humans, such heat exchangers are the hands and feet. Thus, from 7 to 80% of the heat from the main metabolism can be removed through the brushes, despite the fact that the brushes make up only 6% of the mass. human body. If necessary, blood circulation in the fingers can increase 600 times.

4. In a calm state, a person loses from 500 to 800 ml of sweat per day, and with it 500 kcal of heat. With breathing, a person releases about 500 ml of water daily.

5. Sweating happens all the time. Even in the complete absence of visible sweating, at least 500 ml of water evaporates through the skin per day - invisible sweating.

6. Evaporation of 1 liter of sweat in a person weighing 75 kg can lower body temperature by 10 ° C.

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3. Secretory (producing) function

The producing function of the skin includes:

Production of sebum by the sebaceous glands;

The secretion of sweat by the sweat glands;

Production of keratin by epidermal cells - keratinocytes;

Productionimmune cells of a number of important biologically active substances involved in immune and inflammatory reactions of the skin.

Thanks to the activity of the sweat and sebaceous glands located in the dermis, the skin creates additional protection in the form of a thin surface film with an acidity of 3.8 to 5.6 pH - the so-called hydrolipid mantle of the skin. This shift in pH to the acidic side serves as an additional protective barrier against infection: in an acidic environment, bacterial reproduction is disrupted. In addition, the thinnest film that is formed by mixing fat and sweat moisturizes the skin surface, maintains the water-salt balance, and also protects the skin surface from overdrying, chapping, etc.

Sebaceous glandsare located throughout the skin everywhere, with the exception of the skin of the palms and soles, and, in the vast majority, are associated with hair follicles, into which they secrete their secret. They can differ significantly in size, localization and structure in different parts of the skin. Most of the large sebaceous glands are in the scalp, on the cheeks and chin (400-900 glands per 1 cm 2).

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

WITHal glands located in areas of the skin devoid of hair (lips, glans penis, clitoris, labia minora, nipples and areolas of the mammary glands), are called free and secrete directly onto the surface of the skin. The regulation of the function of the sebaceous glands is carried out with the help of the autonomic nervous and endocrine systems.

The sebaceous glands secrete about 20 g of sebum per day, which has many functions: it gives elasticity to the hair, softens the epidermis (protects the skin from maceration in the fetus), regulates the evaporation of water and the excretion of some water-soluble metabolic products from the body, prevents the penetration of substances from the environment into the skin. environment, has an antimicrobial and antifungal effect. In addition, substances toxic to the body are released with sebum, as well as many medicinal substances - antibiotics, quinine, iodine, bromine, antipyrine, salicylic acid, ephedrine, etc.

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1. Most of all sebum is secreted by the skin of the scalp, forehead, cheeks, nose (up to 1000 sebaceous glands per cm 2), central chest, interscapular region, upper back and perineum.

2. Oily skin, which at a young age can create a lot of problems, with proper care, keeps it young and fresh look than dry. After all, it is in people with oily skin that they begin to manifest later age-related changes.

3. Female sex hormones (estrogens) inhibit and male sex hormone (testosterone) stimulates sebum secretion.

4. Increased activity of the sebaceous glands is characteristic of oily skin, which is regulated by the level of sex hormones. That is why in youth, during puberty and the maximum concentration of sex hormones, the skin, as a rule, is more oily. In menopause and menopause, the level of hormones, and with it the fat content of the skin, decreases sharply and a tendency to dryness and flaking appears.

5. Oily skin is one of the 4 normal options (dry, normal, oily, combination). It is characterized by the presence of greasy shine and enlarged pores. Severe oily skin is a pathology called seborrhea. In this condition, not only the secretion of sebum is increased, but also its qualitative composition is changed: bactericidal properties are reduced and the content of unsaturated fatty acids is insufficient. When comedones regularly appear against the background of seborrhea (black and white dots, indicating blockage of the ducts of the sebaceous glands) and pustular elements, this is already acne.

6. In absolutely all people, the activity of the sebaceous glands varies depending on the hormonal level, however, the degree of their sensitivity is an individual, genetically determined feature. In other words, the oiliness of the skin will differ in different people with the same hormone levels.

7. In women, the oiliness of the skin can vary significantly depending on the phase. menstrual cycle as well as during pregnancy.

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

sweat glandsare small tubular structures located in the human skin that produce sweat. The secretory activity of the sweat glands is controlled by the autonomic nervous and endocrine systems. There are two types of sweat glands: exocrine and apocrine.

E xocrine sweat glands are smaller than apocrine. They are located more superficially and exude sweat directly on the surface of the skin. They are located on the entire area of the skin, with the exception of the head of the penis, clitoris and lips. The density of sweat glands in different parts of the body can vary greatly. Most of them are on the soles, palms, scalp, in the armpits, on the chest (more than 250 glands per cm 2). Exocrine sweat glands begin to work from birth, respond to temperature fluctuations in both the body and the environment.

A Pocrinal ("sex") sweat glandslarger, located in the armpit, in the nipples, navel, genitals, and secrete their secret into the hair follicle. These glands respond to stress, joy, pain, sexual arousal, that is, emotional stimuli. Their thick secret contains substances (volatile fatty acids, essential compounds, hormones, pheromones) and determine the individual smell of a person.

A Pocrinal glands finally mature and begin to work actively during puberty, maintaining their activity throughout the entire reproductive period of life in both men and women, fading away with the onset of menopause. Their activity can be disturbed even at a young age with exhaustion and a decrease in the general metabolism, depending on starvation, debilitating disease, etc.

WITH there is a close relationship between the activity of the apocrine glands and certain moments of sexual life (sexual arousal, menstruation, pregnancy, menopause). For example, their activity and secretion may increase in women during menstruation and pregnancy. In the first case, this is explained by the increased sexuality of a woman in this period, which corresponds to the maximum of the emitted "sexual" smell; in the second - a general increase in metabolic processes in the body, expressed in hypersecretion of other skin glands (mammary, sweat, sebaceous and paraurethral).

Z apah and the composition of sweat depends on the state of human health, as well as on the food consumed. Sweat is based on water - 98-99% - to which nitrogenous substances are added: urea, uric acid, creatinine and ammonia (the result of protein breakdown), amino acids serine and histidine, volatile fatty acids and their compounds, cholesterol. Ions: sodium, potassium, chlorine (give a salty taste), calcium, magnesium, phosphorus, iodine, copper, manganese and iron. In addition, there is urocanic acid, glucose, vitamins, steroid hormones, histamine and a number of other organic components. With sweat, not only excess water and salts are released, but also substances that are toxic to the body: with low salt intake, sweat will become less salty, in patients diabetes in sweat, the content of glucose is increased, in case of a diseased liver - bile acids. With significant physical stress, milk is excreted with sweat. acid.

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

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1. Three million sweat glands located on the human body will take 6 kilometers if you have the patience to stretch them in one line.

2. Women sweat less than men.

3. Surprisingly, freshly excreted sweat is almost odorless, and even apocrine glands supply the environment with a light, pleasant, individual smell for each of us. However, as a result of the vital activity of bacteria living on the surface of the skin, sweat quickly decomposes, as a result of which it appears. bad smell degradation of proteins and fatty acids.

4. Smell male sweat different from women. This is due to the fact that on the skin of women and men live different kinds microorganisms, which determines the difference in the smells of male and female sweat and the process of sweating.

5. Sweat glands produce from one to four glasses of sweat per day, and with it 500 kcal of heat. At their maximum functional activity, up to 3 liters of sweat per hour is released, which can quickly lead to dehydration.

6. If there was no sweating, then every 5 minutes the body temperature would rise by 10 0. And in half an hour, when the body temperature would reach 42 0, the person would die from overheating.

7. Wet skin sweats less intensely, which is associated with swelling of the stratum corneum and narrowing of the mouths of the sweat glands. In the armpits, this effect is not present.

4. Excretory (excretory) function

I is an addition to the previous function. Due to the excretory function, through the pores of the skin, together with sweat and sebum, excess water (up to 800 ml), salts, metabolic products and toxic substances are released. This means that the skin, along with the kidneys, lungs and digestive system, is an excretory organ.

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

5. Respiratory function

TO The skin has the ability to absorb oxygen and remove carbon dioxide from the body, but compared to the lungs, the participation of the skin in respiration is small. The skin absorbs 1/180 of the oxygen and releases 1/90 of the pulmonary carbon dioxide exchange.

D skin respiration is activated with an increase in air temperature, physical exertion, an increase in the oxygen content in the air, with the functioning of the digestive system, inflammation of the skin, etc. So, when the air warms up to 40⁰ C, the intensity of oxygen absorption increases by 2.5-3 times. With an active muscular load, the saturation of the body with oxygen through the skin doubles.

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1. An increase in the thickness of the epidermis reduces the intensity of gas exchange in the skin.

2. The body and head "breathe" most intensively, and the gas exchange of the skin of the arms and legs is lower.

3. In children, gas exchange through the skin is greater than in adults.

6. Resorption (suction) function

H Some substances can penetrate the skin, including poisons, and medications. It should be noted that the skin of the palms and soles of the feet are characterized by a weak suction capacity due to physiological hyperkeratosis (thick layer of the epidermis) and the absence of sebaceous and sweat glands in them. The resorption properties of the skin are well manifested in those areas of the body where there are many sebaceous and sweat glands, as well as a thin stratum corneum.

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1. With inflammatory changes in the skin, absorption through the skin is activated.

2. Fat-soluble substances are absorbed especially well by the skin.

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

7. Sensitivity sensor function

H being in maximum contact with the outside world, the skin, along with other sense organs (smell, sight, hearing) informs a person about changes in the external environment, potential or real danger. Numerous sensory receptors located on the surface of the skin inform the brain by sending impulses about pain, tactile (touch, blow), temperature (cold, heat, heat) stimuli, as well as air movement, pressure, etc.

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1. The entire receptor field of the skin plays an important role in the motor function of a person, since it supplies the brain with information about the space surrounding it. When moving, a person feels the surface on which he walks, its strength, touches objects, feels air vibrations, which affects the sense of balance, orientation, and coordinated muscle work.

2. Tactile sensitivity most pronounced in the skin of the terminal phalanges of the fingers: smoothness, roughness, elasticity, softness, etc.

3. Heat and cold receptors are unevenly located in the skin, so the perception of heat and cold is different in different parts of the skin. There are much more cold points on the entire surface of the skin than thermal ones.

Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

8. Immune defense function

IN a single-lipid film created by the glands of the skin, as well as immune cells of the epidermis and dermis (mast cells, phagocytes (giant Langerhans cells, macrophages, basophils, eosinophils, neutrophils), T-lymphocytes), are the first barrier to infection and prevent penetration into organism of harmful bacteria, microbes and viruses. In addition, they recognize and destroy their own old or damaged cells. Certain types of immune cells mature in the skin and immune responses take place. Keratinocytes directly secrete biologically active substances involved in immune and inflammatory processes, as well as contributing to the maturation of T-lymphocytes.

There are 2 types of immunity in our body:

- non-specific (it is also congenital) - its cells recognize and react to any foreign agents, but long-term specific immune protection is not created.

Specific (acquired, expressed in the formation of highly specific killer cells or antibodies to a specific foreign antigen, which will persist throughout life and destroy it faster and more efficiently upon repeated collision). So in people who once had chickenpox, rubella, measles, diphtheria, lifelong immunity to these diseases is formed.

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If the skin, as a mechanical barrier covered with an acid film, cannot cope with an infection that penetrates the skin, then immune cells enter the battle, providing an immune response - detection and removal of antigens (foreign agents).

With any penetration of an infectious agent into the body (skin, Airways, digestive system) to the site of damage from the blood or surrounding tissues migrate to in large numbers phagocytes that recognize and destroy foreign particles by phagocytosis (swallowing and subsequent intracellular digestion), and then fragments of a foreign agent are placed on their surface like an antenna. After that, a T-lymphocyte attaches to the phagocyte and takes the fragment, while specifically changing - a receptor appears on its surface, which will mirror reflection absorbed antigen. Now, when meeting with the same foreign agent, the T-lymphocyte instantly recognizes and destroys it. In addition, the T-lymphocyte passes the fragment to the B-lymphocyte, which begins to produce antibodies - proteins that will also specifically bind to the antigen and destroy it.

9. Exchange function

I is a combination of secretory, excretory, respiratory and resorption functions.

R The role of the skin in all metabolic processes of the body (protein, carbohydrate, lipid, water-electrolyte) can hardly be overestimated, which is associated with its large depositing (accumulating) capacity.

Connective tissue cells, collagen, elastin fibers, hyaluronic acid present in the dermis and hypodermis, as well as subcutaneous adipose tissue, are highly hydrophilic, i.e. the ability to bind and retain water. This feature ensures the retention of intracellular and extracellular fluid, vitamins and microelements. In other words, the skin is able to quickly accumulate - give away water and salts, and in terms of the activity of water-mineral and carbon dioxide metabolism, the skin is second only to liver and muscles. On the other hand, with a decrease in the diet (for example, starvation or diet) becomes a source of nutrients for the normal functioning of the body.

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1. The skin and subcutaneous fat are able to accumulate carbohydrates, amino acids, cholesterol, iodine, bromine, bile acids and toxins - substances that are formed during metabolism, but the body cannot neutralize and remove them. That is why, long before clinical manifestations general metabolic disorders in a particular system or organ, a number of pathological symptoms and processes. For example, the appearance of allergic rashes and persistent itching in violation of the function of the liver, pancreas and digestive system or persistent pustular elements, hidradenitis, folliculitis, fungal diseases in the presence of undiagnosed diabetes mellitus.

2. Vitamin D is produced in the skin, which is necessary for the normal growth and development of children, and also ensures the strength of the skeletal system in adults.

The condition of the skin, its external attractiveness and health are a significant factor in social relations between people and sexual attractiveness. well-groomed, healthy skin is the key to success in today's society. Acquaintance with the structural features of the skin, its functions and features will help to prevent its problems in a timely manner, with the help of competent and timely care.

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Not a public offer! There are contraindications. Before use, a specialist consultation is necessary.

In the skin there is an outer layer - the cuticle, and behind it are the actual skin and subcutaneous tissue. Skin cells have different structures and functions. All together they protect the body from mechanical, thermal effects, ultraviolet radiation.

Read in this article

Structure of skin layers

The skin is made up of several layers containing cells different form, structure and purpose.

The structure of the epidermis

The cuticle is composed of keratin, pigment and immune cells. All of them are arranged in layers, the thickness of these layers is maximum on the palm, sole, and the eyelids and genitals have the thinnest epidermal membranes. The epidermis includes the following parts:

basal,
prickly,
grainy
shiny,
horny.

The structure of the epidermis

The deepest layer is the basal layer. It has only one row of cylindrical cells, which unusually divides to replace dead ones. In this case, one maternal cell is always mobile and forms the germ layer itself, and the second cell rises upward from the depths. In the process of moving, it changes its shape and structure - it becomes overgrown with spikes, becomes flat and contains grains of keratohyalin, eleidin, insoluble keratin is synthesized from them.

The most top part epidermis - these are horny scales that do not have a nucleus, they peel off from the surface. Pigment cells produce melanin to protect against ultraviolet radiation, and "guards" are located in the spiny layer immune systems s are macrophages that eliminate foreign compounds absorbed into the skin.

What do skin cells do

The skin layer itself is called the dermis, it consists of fibers, ground substance and cells. There are relatively few of the latter, since the main role of this part is the support one. The dermis has two layers. The upper one is papillary, it penetrates the epidermis in the form of loose connective tissue fibers that form a pattern, it is best seen on the fingers and palms. Inside the papillae are vessels, nerve endings.

The lower mesh layer is thicker, in which the coarse fibers of the tissue run parallel to the surface of the skin. It is they who determine the strength of the skin in different parts of the body.

The role of the subcutaneous tissue

Accumulations of fat cells form the subcutaneous layer. This fabric is designed to retain heat and store energy in the form of fat. With a deficiency in the intake of glucose or a violation of its absorption, it is fat that becomes a substance that ensures vital activity. The largest layer is located on the buttocks, it reaches 10 cm, and the thinnest of all is this layer on the skin of the skull - its transverse size is 2 cm.

Skin appendages

They are formed by hair, nails, glands for removing sweat and sebum. The sweat glands are located at the very depth of the dermis and look like a glomerulus with a long duct. They remove liquid, salts, metabolic products with sweat, regulate the temperature.

Sebaceous glands- these are bubbles covered inside with epithelium, it is gradually destroyed, forming fat as a result of fatty degeneration.

What are the functions of human skin

Integuments provide human survival in the environment. This is possible due to protection, thermoregulation, immune resistance, sensitivity, respiratory function.

Protective

This is the main role. It is implemented in several ways. Mechanical resistance provides a dense stratum corneum. Elasticity, resilience and ability to shock absorption are possible due to subcutaneous tissue. The role of absorption of ultraviolet radiation that is detrimental to the body is performed by melanocytes, which give more dark color epidermis.

The water-fat shell is formed due to the work of the sweat and sebaceous glands. It does not allow penetration of microbes, chemical compounds. Normally, the skin is impervious to a huge number of bacteria, fungi and viruses that are constantly on its surface. They are removed by sebum, sweat, epidermal flakes and acidic environment water-lipid mantle.

Constant temperature regulation

Almost 80% of all generated heat is lost through the skin by thermal radiation, sweat release and evaporation. The regulator of the intensity of this process is the subcutaneous tissue. It does not allow excessive overheating and hypothermia of the body. In hot weather, the vessels of the skin expand, blood circulation in them increases, sweating increases. When the ambient temperature drops, the reverse reaction occurs.

Secretory

The glands of the skin can produce sweat under the influence of external heat, physical activity, internal activity of the parasympathetic nervous system, infectious processes. During rest and during sleep, sweating decreases.

The second route of excretion is the secretion of the sebaceous glands. Salo is 65% water, and 35% salt, fatty acids, organic compounds, including the metabolic products of sex hormones. The activity of the sebaceous glands increases in adolescents, reaches a maximum by 23-25 years, and then decreases.

With skin secretions, substances are released into the environment that form sex drive. They are called pheromones and through the sense of smell can affect sexual function. Therefore, the smell of a loved one is pleasant, and the expression “I can’t stand it” has a biological meaning.

There is also a vitamin-producing ability of the skin to synthesize and accumulate vitamin D under the influence of sunlight.

Respiratory

Due to the location on the surface of the network of blood, lymphatic vessels, nerve endings, skin type of breathing is carried out. It accounts for only 2% of the total gas exchange of the body, but 1 cm3 of skin per day absorbs more oxygen than the same volume of lung tissue, providing itself with it on its own.

Skin sensitivity

Great value for contact with outside world have skin receptors. They respond to pain, cold, heat, pressure. There are almost 5000 of them per 1 cm 2. The maximum density of nerve endings is on the face, fingers, hands, genitals. Through them, the perception of the environment and the transfer of information about it to the brain occurs.

Function of melanin

Pigments with a complex chemical composition are found not only in the skin. They give color to the hair, the iris. They have even been found in the inner ear and brain. Cells for the synthesis of melanin are called melanocytes. The pink color of the lips, genitals, nipples depends on their work.

But coloring is not the main function of melanin, it has the ability to absorb ultraviolet light, inhibiting its penetration deep into the skin. This compound has also been found to have other unusual functions:

reduces excessive emotionality, aggressiveness;
prevents the formation of ulcers and erosions in the stomach;
slows down weight loss in a stressful situation;
absorbs uranium, preventing it from accumulating in the body;
protects against the genetic consequences of exposure;
exhibits very high antioxidant activity.

The skin consists of the epidermis, the dermis layer and the subcutaneous tissue. All cells have a different structure and functional significance. With the help of the skin, the body is protected from external influences, thermoregulation, breathing, sensations of pain, heat, cold, pressure. Melanin prevents the penetration of ultraviolet radiation deep into the skin, and macrophages stop microbes and toxic compounds.

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4. Excretory (excretory) function is carried out by the sebaceous and sweat glands of the skin. The secret of the sweat glands and sebum have a slightly acidic reaction. Sebum is composed of free and bound fatty acids, glycerol, free cholesterol and its esters. In the composition of the secretion of the sebaceous glands, nitrogenous and phosphorus compounds. With sebum, some medicinal and toxic substances are excreted from the body.

Sweat glands that secrete sweat remove excess water, inorganic (sodium chloride, potassium chloride, sulfates and phosphates) and organic (uric acid, urea, ammonia, etc.) substances from the body. Sugar is excreted in diabetic patients with sweat.

In people suffering kidney failure, sweat glands partially perform the excretory (excretory) function of the kidneys. The sweat glands can also excrete drugs. The secret of these sweat glands, in addition to the usual components, contains cholesterol, cholesterol esters, glycogen, iron, sulfur.

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

Chemical reactions take place in the skin, which begin and/or end in other organs and systems. Many substances are synthesized here, such as melanin, vitamin B, keratin, sebaceous secretions, and some enzymes.

One of the main functions of the skin is to protect the body from harmful effects environment. The skin protects the body from mechanical damage(bruises, cuts, pressure), regulates body temperature, protects against radiation effects (infrared, ultraviolet rays, etc.). The coloring matter of the skin - the pigment - prevents the harmful effects of sunlight: sunburn protects the skin from their enhanced effect. The density of the epidermis, the elasticity of the skin and subcutaneous adipose tissue prevents the possibility of mechanical damage and reduces their strength. The skin produces sweat and sebum. Sebum, lubricating the skin, prevents it from soaking and the formation of cracks and abrasions, which protects the skin from the harmful effects of water and various chemical compounds.

The skin contains nerve endings and nerve apparatus that perceive temperature irritations. Cold is perceived faster than heat. However, both cold and heat are felt differently on different parts 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 feels a difference in temperature by 0.5 ° C.

The skin has bactericidal properties, which protects the body from the penetration of microbes with intact skin. It is also able to produce protective substances against various infectious diseases.

A special role is given to the respiratory function of the skin. The skin releases carbon dioxide and absorbs oxygen, resulting in gas exchange, which is about 2% of the total body gas exchange. Skin respiration and redox processes are closely related and depend on the functions of the sweat glands.

The skin is an organ of thermoregulation: 80% of heat transfer occurs through the skin by radiation, heat conduction and evaporation of sweat. It regulates the exchange of heat between the body and the external environment. Thermoregulation depends on the nervous system. Irritation of the nerves causes expansion or constriction of blood vessels; when contracting, heat is retained in the body, when expanding, a greater heat transfer occurs. Sweat glands play a significant role in heat transfer. On average, a person produces from 600 to 900 ml of sweat per day. Evaporation from the surface of the skin causes a decrease in body temperature. With a decrease in external temperature, heat transfer decreases, with an increase, it increases.

Thermoregulation of the body is carried out in various ways. The skin performs the same function as a car radiator - it cools the blood by exposing it to the external environment, the temperature of which is lower than the temperature inside the body. In this case, the capillaries in the skin expand and fill with blood. Blood cools on the surface of the skin, circulates throughout the body, lowering its temperature. that mechanism works when we are hot. Conversely, when it's cold, the capillaries constrict, causing the opposite effect. This explains why we blush when it's hot and turn pale when it's cold.

It is important to know about the absorption (absorption) function of the skin. Water and salts dissolved in it are not absorbed by the skin, since the lustrous and stratum corneum are impregnated with lipids, which prevent them from penetrating into the skin. However, water-soluble substances can be absorbed through the sebaceous hair follicles and excretory ducts of the sweat glands, and various fat-soluble substances through the epidermis. You should know that the biologically active substances (vitamins, hormones, extracts) included in creams are quite easily absorbed by the skin and affect not only locally, but also on the body as a whole.

The skin is actively involved in the overall metabolism of the body. Currently, cosmetologists have studied the effect of creams with biologically active substances on metabolic processes and revealed patterns of their change. So, the systematic use of creams, masks, massage contributes to the regulation of metabolic processes.
Summing up

The main functions of the skin:

- first of all, the skin is a mirror of the health of the whole organism - the condition of the skin can determine the diseases that a person suffers from;

- a protective barrier against the penetration of external infection - a dense upper layer of the epidermis and a surface layer of fatty acids (lipid layer), which forms the surface electrical potential necessary for the normal functioning of the skin;

- depreciation function of the skin due to the mesh and fat layers that protect the body from concussions;

- excretory function: sweat glands secrete about 40 grams of salt per day, and sebaceous glands - 300 grams of fat per week; in dry and hot climates, the sweat glands secrete a lot of fluid, which facilitates the work of the excretory organs - the kidneys;

- participation in gas exchange: 2 times more water vapor is released through the skin than through the lungs;

- participation in heat exchange: the optimum ambient temperature is 18-20 degrees Celsius; the skin actively reacts to both an increase and a decrease in temperature;

- tactile function: sensitivity to temperature, mass, pain, touch, since the skin is directly connected with the nervous system;

- absorption capacity of the skin: through the pores to the vessels. The epidermis itself is a very dense defense through which nothing penetrates. Therefore, before Neways, skin creams were absorbed only in the amount of 20%. With the advent of Neways, transdermal penetration products are being developed that are so low in molecular weight that they can penetrate the epidermis.

The skin contains 60-70% water, the fatty layer contains 10% water. The dermis itself is 90% collagen. The skin needs vitamins D, B, E, C, moreover, A and E are called beauty vitamins, and the group A, E and C is an antioxidant that slows down the aging process.

The skin is the outer covering of the body and performs a complex set of physiological functions. It is actively involved in the process of metabolism, especially water, mineral, fat, carbohydrate, vitamin and energy. The skin is a huge depot of carbohydrates, toxins, circulating immune complexes, antigens, antibodies and other products of general and tissue metabolism. Participating in all vital processes of the body, the skin performs a number of important special functions. functions: immune, protective, secretory, receptor, etc.

The skin is an immune organ. Healthy skin and intact mucous membranes are a barrier to most microorganisms, with the exception of those with a special penetration apparatus. This protective function of the skin was previously explained only by mechanical factors - the stratum corneum, water-lipid mantle, high elasticity and subcutaneous fatty tissue. However, at present, there is information about the immune activity of the main structures of the skin that implement the immune response: the epidermis, dermis, and subcutaneous fatty tissue.

Due to the fact that T-lymphocytes are the main element of the immune system, the anatomical, molecular and functional similarity of epidermal keratinocytes with epithelial cells of the thymus has been proven. These include epidermal thymocyte-activating factor (ETAF), interleukins-1, 2 (T-cell growth factors), interleukin-3 (mast cell proliferation and degranulation factor), natural killer activating factor (FANK), epidermal granulocyte activity factor . In addition to them, keratinocytes produce a number of nonspecific mediators, biologically active factors involved in the immune and inflammatory reactions of the skin. Among them, the most studied are fatty acid metabolites (prostaglandins, leukotrienes, fatty acid hydroxides), plasminogen activator and inhibitor.

Keratinocytes promote the maturation of T-lymphocytes by the action of deoxynucleotidyltransferase. epidermal cells

able to induce the expression of this enzyme, as well as the secretion of thymopoietin in the process of T-lymphocyte differentiation. The important role of epidermal cells in immune processes in the skin is also confirmed by their ability to express immunoassociative antigens (HLA-DR) on their surface. Some researchers believe that these receptors facilitate the migration of white process epidermocytes into the skin, others believe that with their help, keratinocytes can present antigen and interact directly with lymphocytes.

The similarity of keratinocytes to thymic epithelial cells is confirmed by common heteroantigens found in the basal cells of the epidermis and the hormonal epithelium of the thymus. The common morphological features of these organs were established during the cultivation of the thymus epithelium. It turned out that thymus cells, when cultivated in the medium, turn into typical epidermal keratinocytes. Subsequently, an antigen characteristic of the cells of the basal layer of the epidermis was found in the receptors of the thymus bodies (Hassal bodies). In the deeper structures of the thymus bodies, antigens characteristic of the prickly, granular and stratum corneum of the epidermis were identified, which allows us to consider the epidermis as an organ functionally similar to the thymus gland.

In the dermis, immune activity is mediated by lymphocytes around postcapillary venules of the superficial choroid plexus and skin appendages. Immunomorphological methods have established that T-lymphocytes make up 90% of all skin lymphocytes and are located mainly in the epidermis and upper layers of the dermis. B-lymphocytes are found in the middle and deep layers of the dermis. The lymphocytes of the perivascular areas consist of almost the same number of helpers and suppressors, and the helper-suppressor index is 0.93-0.96. Most of these cells are in an activated form, which is confirmed by the detection of immunoassociative antigens (HLA-DR) and interleukin-2 receptors on their surface.

Endothelial cells of postcapillary venules of the superior vascular plexus and the macrophage system play a significant role in the development and formation of skin immune responses. The macrophage system is represented in the dermis and subcutaneous adipose tissue by fibroblasts, phagocytic macrophages (histiocytes), and dendritic cells. Morphologically differentiated tissue histiocyte is a process cell with a large number of

microvilli. Histiocytes contain RNA and enzymes in the cytoplasm. On the surface of histiocytes, like all macrophages, there are receptors for C3 and the Fc fragment of lgG. The macrophage system of the skin also includes mast cells involved in the migration of T-lymphocytes in antigen-antibody reactions of the type of immediate hypersensitivity. The implementation of immune processes in the skin also involves blood cells migrating into the skin (monocytes, eosinophils, neutrophils, basophils, erythrocytes), which perform various immune functions, the basis of which is the interaction of T-lymphocytes with nonspecific defense factors.

The immune function is also performed by white process epidermocytes, which are an altered variety of the population of tissue macrophages. Like mast cells, fibrocytes and macrophages, these cells do not have immune specificity, but when activated by antigens or cytokines, they exhibit physiological activity with the release of biologically active substances.

protective function. The barrier properties of the skin as an organ of mechanical protection are provided by significant electrical resistance, the strength of collagen and elastic fibers, and elastic subcutaneous fatty tissue. The skin is protected from drying out by a compact stratum corneum and a water-lipid mantle located on the surface of the skin. The stratum corneum is resistant to many chemical and physical damaging effects.

The protective function of the skin against microbial flora is very important. This is facilitated by the rejection of keratinized epithelium and the secretion of sebaceous and sweat glands. In addition, the skin has sterilizing properties due to the acidic reaction of the water-lipid film, which simultaneously inhibits the absorption of foreign substances. At the same time, the water-lipid mantle of the skin prevents the penetration of microorganisms, and the low molecular weight fatty acids contained in it have a depressing effect on the growth of pathogenic flora (“its own sterilizer”).

Chlorides are present in the skin in a significant amount, more than 2 times the content of this anion in muscle tissue. It is believed that this is a means of protection against pathogenic microorganisms. In the presence of myeloperoxidase, localized in the azurophilic granules of neutrophils and monocytes, hypochlorite is formed from chlorine and hydrogen peroxide, which destroys the structure of the microbial membrane, which leads to the death of the organism.

The protective function of the skin is also carried out by proteoglycans, which consist of polysaccharides (95%) and protein (5%) units. These polyanions, which have very big sizes, bind water and cations, forming the main substance of the connective tissue. Proteoglycans act as a molecular sieve for substances diffusing in the extracellular matrix: small molecules penetrate the network, while large ones are retained.

The mucous membrane of the mouth, whose structure is similar to the structure of the skin, also performs protective functions, although to a lesser extent. This is facilitated by the constant wetting of the oral mucosa with saliva, which leads to its supersaturation with water, a decrease in the sweating of the interstitial fluid, and thus makes it difficult for the penetration of microbial flora and foreign substances. The bactericidal properties of lysozyme contained in saliva enhance the protective role of the oral mucosa.

Under the influence of high-energy ultraviolet rays of the sun, free radicals form in the skin. Such molecules easily enter into chemical reactions, including chain ones. Violation of the function of biological membranes, built mainly of proteins and lipids, is one of the most important biological effects of ultraviolet rays. Protection of the body from the damaging effects of the ultraviolet rays of the sun, which lie outside the light visible to the human eye (less than 400 nm), is carried out using several mechanisms. The stratum corneum thickens in the skin, skin pigmentation increases, urocanic acid passes from the trans-isomer to the cis-isomer, enzymatic and non-enzymatic systems of antiradical protection are mobilized. The shielding layer of the pigment either absorbs light of all wavelengths or filters out particularly dangerous rays. Melanin, in particular, absorbs visible light and ultraviolet rays in the entire range.

The more melanin in the skin, the more fully it provides protection from rays harmful to the body. In the skin, a rapid renewal of melanin occurs, which is lost during the desquamation of the epidermis, and then re-synthesized by melanoblasts. The synthesis of melanin is influenced by the hypozysis hormone (melanin-stimulating hormone), an important role is played by tyrosinase, which catalyzes the oxidation of tyrosine, and doxyphenylalanine (DOPA). Biochemical mechanisms of antioxidant defense provide inhibition of free radical reactions at the stages of initiation, branching and termination of oxidation chains.

secretory function. This function is carried out as a result of the secretory activity of keratinocytes, immunoregulatory cells, as well as the functional activity of the sebaceous and sweat glands.

The formation of keratin - the main protein of the epidermis - is a complex secretory process, it is carried out by keratinocytes. First stage proceeds in the cells of the basal layer, where keratin fibrils appear in the form of tonofilaments. In the cells of the spiny layer, the protein of tonofilaments is converted into α-keratin, similar to prekeratin - actomyosin.

More specific structures are observed in the cells of the granular layer. Keratohyalin granules appear in them, which contain fibrils. Fibrils turn into eleidin, and then into filaments of keratin, which forms the basis of the cells of the stratum corneum. As cells move from the basal layer to the upper layers of the epidermis, the nuclei and other cell organelles keratinize into tonofilaments, which gradually form protoplasm protein into keratin.

Growth and reproduction of epidermal cells in normal physiological conditions are under the influence of complex mutually competing extracellular and intracellular factors. Intracellular mediators mediating the action of hormones and other biologically active substances on cell mitosis include cyclic nucleotides, prostaglandins, chalones, leukotrienes, interleukins (especially IL-1 and IL-2) and calcium ions, which affect the activity of phosphodiesterase and cAMP to cGMP ratio. The epidermal growth factor significantly affects the intracellular control of mitosis. This polypeptide has a hyperplastic effect on epithelial tissues. Its activity depends on the function of the pituitary-adrenal system.

Thus, the state of complex physiological system- corticosteroid hormones and adrenaline in cooperation with intracellular mediators, including phosphodiesterase, adenylate cyclase, cAMP and cGMP - determines the activity of epidermal growth factor and its effect on the secretion of keratin by epidermocytes. Important role in the implementation of the secretory function of the skin play sebaceous and sweat glands.

The sebaceous glands produce sebum, which is composed of fatty acids, cholesterol esters, aliphatic alcohols, small amounts of carbohydrates, free cholesterol, glycerol, and small amounts of nitrogenous and phosphate compounds. In the sebaceous glands

the secret is in a liquid or semi-liquid state. Standing out on the surface of the skin and mixing with sweat, sebum forms a water-lipid mantle. It protects the skin, has bactericidal and fungistatic activity. It is believed that the sterilizing effect of sebum is due to the content of free fatty acids in it. In addition to secretory, the sebaceous glands also perform an excretory function. With sebum, toxic substances formed in the intestines, medium molecular weight peptides, as well as many medicinal substances - iodine, bromine, antipyrine, salicylic acid, ephedrine, etc.

The amount of sebum produced is different for each person, it is uneven in different parts of the skin. So, the largest amount of sebum is released on the skin of the scalp, forehead, cheeks, nose (up to 1000 sebaceous glands per 1 cm 2), in the central part of the chest, interscapular region, upper back and perineum. The function of the sebaceous glands is regulated by the endocrine and nervous systems. Testosterone and related substances stimulate, while estrogens suppress the secretion of sebum.

The sweat secreted by the eccrine sweat glands is slightly acidic. In addition to water, it contains a small amount of dissolved inorganic (sulfates, phosphates, sodium chloride, potassium chloride) and organic (urea, uric acid, ammonia, amino acids, creatinine, etc.) substances.

The chemical composition of sweat is not constant and can vary depending on the amount of fluid drunk, emotional stress, mobility, general condition of the body, ambient temperature, and also depends on the topography of the sweat glands. Sweat from the forehead contains 6-7 times more iron than sweat from the skin of the hands or feet. The content of chlorides in sweat depends on the rate of sweating, metabolic rate, skin temperature and age of the person. Medicinal substances - iodine, quinine, antibiotics - can also be excreted from the body with sweat. On average, 750-1000 ml of sweat is released per day, but at high temperatures several liters of sweat can be excreted. In the regulation of the activity of the sweat glands, the leading role belongs to the central and vegetative nervous system. The main stimulator of the activity of these glands is an increase in external temperature.

The excretory function of the skin is combined with the secretory. In addition to the secretion of organic and inorganic substances by the sebaceous and sweat glands,

substances, products mineral metabolism, carbohydrates, vitamins, hormones, enzymes, trace elements and a significant amount of water are removed from the body. Sweat is released constantly and continuously. Distinguish invisible sweating in the form perspiratio insensibilis and profuse, occurring with increased thermoregulation.

The function of the apocrine glands is related to the activity of the gonads. They begin to function with the onset puberty and stop their function in menopause. Apocrine glands, as well as sebaceous and sweat glands, respond to emotional, endocrine dysfunctions, stressful situations and changes in the thermal regime.

Respiratory and resorption functions. The resorption properties of the skin depend on the functional activity of the sebaceous hair follicles, the state of the water-fat mantle, and the strength of the stratum corneum. The surface of the palms and soles has a weak resorption capacity as a result of physiological hyperkeratosis. In places where the sebaceous and sweat glands are abundant, the stratum corneum is weakly expressed, the resorption properties of the skin are enhanced: medicines soluble in fats - iodine, phenol, pyrogallol, resorcinol, salicylic acid, boric acid and others. With inflammatory changes in the skin, resorption processes are activated, therefore, drugs for external use should not exceed therapeutic concentrations. Participation of the skin in respiration, i.e. uptake of oxygen and release of carbon dioxide is negligible. The skin absorbs 1/180 of the oxygen and releases 1/90 of the pulmonary carbon dioxide exchange.

thermoregulatory function. Adaptive mechanisms that maintain a constant body temperature are diverse. In addition to the reduced thermal conductivity of the stratum corneum of the epidermis, the fibrous substances of the dermis and subcutaneous fatty tissue are essential. An even more significant influence on thermoregulation is exerted by the state of blood and lymph circulation and the excretory capacity of the sebaceous and sweat glands.

The sweat glands that produce sweat cool the skin by evaporating it to maintain a constant body temperature. Evaporation of sweat is an energy-intensive process: the evaporation of 1 liter requires 2400 kJ, which corresponds to 1/3 of the total heat generated at rest for the whole day. The activity of the sweat glands is mainly regulated by the temperature factor in the skin of the trunk, the back surface of the hands,

extensor surface of the forearms and shoulders, neck, forehead, nasolabial folds. Heat transfer by heat radiation and evaporation is increased with vegetodistonic and dyscirculatory disorders.

exchange function. The role of the skin in metabolism is especially significant because of its deposition ability. The hydrophilicity of connective tissue cells, elastic, collagen and argyrophilic fibers, subcutaneous adipose tissue causes a delay in intracellular and extracellular fluid and minerals, vitamins, microelements. Carbohydrates, cholesterol, iodine, bromine, amino acids, bile acids and slags formed in the process of lipid peroxidation are deposited in the skin. In this regard, long before general metabolic disorders in the skin, a number of pathological processes occur in the form of persistent itching in case of impaired liver function or persistent pyogenic elements in latent diabetes mellitus.

Many chemicals that have penetrated into the stratum corneum remain in it for a long time. The administration of prednisolone labeled with a radionuclide by percutaneous iontophoresis made it possible to detect the drug even 2 weeks after local iontophoresis, and when taken orally, it is detected only for 24 hours.

vitamins have a great impact on the condition of the skin. In particular, B vitamins that support normal flow redox processes, vitamin PP (nicotinic acid), which promotes the elimination of metabolites and detoxification, vitamins A, E, D, being anti-infective factors, activate protein metabolism, normalize the process of keratoplasty in the epidermis, and promote epithelial regeneration during inflammatory processes.

receptor function. The skin not only protects the body from various influences, but is also a multifactorial analyzer, as it is an extensive receptor field. The receptor functions of the skin are provided by a wide variety of sensitive nerve endings and sensory bodies, dispersed unevenly throughout the skin. There is tactile (sense of touch and pressure), pain and temperature (sense of cold and heat) skin sensitivity. Tactile sensitivity is most characteristic of the skin of the terminal phalanges of the fingers, the skin in large folds and on the mucous membrane of the tongue. Such sensitivity includes sensations of density, softness and other features of the consistency of objects. Nerve formations that perceive cold and heat (it is assumed that these are Ruffini's bodies and Krause's flasks) are located

in the skin is uneven, so the perception of heat and cold is different in certain areas of the skin.

The mucous membrane of the mouth is also rich in a variety of nerve endings that perceive heat, cold, pain and touch. However, unlike the skin, the sensitivity of all types to less intense stimuli is more pronounced.

The receptor field of the skin functionally interacts with the central and autonomic nervous systems, constantly participates in dermoneurotropic, dermovisceral connections. The skin continuously responds to a variety of stimuli coming from the environment, as well as their central nervous system and internal organs. It is logical to imagine that the skin is like a screen on which functional and organic changes in the activity of internal organs, the central nervous system, the endocrine and immune systems are projected. Often, even with a slight disorder in the activity of the body and its individual functions and systems, changes occur in the skin, sometimes allowing one to confidently assume one or another visceral or endocrine pathology.

In humans, breathing through the skin is negligible. At rest per day, a person absorbs 3-6.5 g of oxygen through the skin, releases 7.0-28.0 g of carbon dioxide. Skin respiration increases with an increase in air temperature, an increase in the oxygen content in the air, during muscular work and digestion. At an air temperature of 40 C, the absorption of oxygen through the skin is 2.5-3 times greater than at normal. During muscular work at an air temperature of 18-20 C, the absorption of oxygen through the skin is 1.5-2 times greater than at rest. The more sweating and the faster the blood circulates through the skin, the more intense the skin gas exchange. Thickening of the epidermis reduces gas exchange. Breathing through the skin in different areas in different areas of the skin is different: on the trunk and on the head it is more intense than on the arms and legs.

Conclusion

The skin protects the body from the harmful effects of various external stimuli.

The stratum corneum significantly reduces pressure, friction and impact. In areas of the body that are repeatedly irritated, the stratum corneum becomes thicker, calluses appear. Due to its mobility and elasticity, the subcutaneous tissue plays an important role in protecting internal organs from pressure and bruises.

In the mechanical protection of the body, the role of collagen fibers of the skin is especially great, which resist rupture 43 times more than elastic ones.

In protecting the skin from electromagnetic waves, an essential role belongs to the skin pigment melanin. The synthesis of melanin is activated by ultraviolet and x-rays. This pigment strongly absorbs ultraviolet rays, so pigmentation of the skin protects against the harmful effects of sunlight on the body.

The skin is much more resistant electric current than the tissues located under it, the stratum corneum has the greatest resistance due to the air content between its cells.

The skin is damaged by acids, alkalis, salts and poisons at their sufficient concentration; much more it resists the action of acids than alkalis. The ability of the skin to neutralize alkalis depends on the intensity of the functions of the sebaceous and sweat glands. Protection against alkalis also depends on the degree of permeability of the stratum corneum. Protein-keratin, located in the stratum corneum, is insoluble in alcohol and ether, resistant to alkalis and acids, well protects the body from many chemicals.

The skin also has sterilizing, bactericidal properties - the ability to destroy microbes. The bactericidal properties of the skin depend on the intensity of metabolism, the content in sebum o and perspiration of lactic and free fatty acids.