What you need to know about human skin. The structure of the human skin: everything about this organ for children

27.08.2019

The body of each person, like other living beings, is covered with a protective layer - dermis. This is the largest organ designed to protect soft tissues and internal organs from external factors. But the dermis is not just a thin layer, because the structure of the skin is complex. Moreover, each ball performs a number of functions and has its own characteristics. The dermis is a multifaceted organ that plays an important role in the normal functioning of the entire body.

The skin is a complex organ that is the outer covering of the body. It performs many functions and ensures the normal functioning of the whole organism.

Doctors have studied in detail the structure of the skin, highlighting 3 main balls:

Today, the structure and function of the skin is still being studied. After all, new technologies promise a lot of unexpected discoveries in the field of medicine and human anatomy.

Modern doctors distinguish such functions that the layers of the skin perform:

Protective.
The dermis protects the body from external factors, UV radiation and invasion of pathogens, as well as from imbalance in moisture.
Thermoregulatory.
Its implementation is carried out by the release of heat and sweat.
Maintaining water-salt balance.
This function is carried out by perspiration.
Excretory.
Its implementation is carried out by sweating. Metabolic products, salts and medicines come out with it.
Blood depositing process.
In the vessels located in the dermis, about 1 liter of this fluid is constantly circulating.
Participation in metabolism and endocrine processes.
Its implementation is carried out due to the synthesis of vitamin D and a number of hormones.
Receptor.
The dermis is one of the most sensitive organs. Its entire surface is covered with hundreds of thousands of receptors that receive information and transmit it to the cerebral cortex.
Immunological.
In the skin, the process of capture, processing and transport of antigen cells is carried out, which is necessary for the appearance of the body's immune response.

Modern biology distinguishes 2 types of dermis:

Thick.
It is rougher and covers the palms, soles of the feet. Its base is a thick epidermis with a layer of 400 - 600 microns. This type is characterized by the absence of hair and sebaceous glands.
Thin.
Its layer, consisting of the epidermis (thickness in the range of 70 - 140 microns), covers the entire body. This type of dermis includes hair follicles and secretory glands.

Modern biology has proven that the skin contains many layers, each of which has a specific meaning. Only such a unique structure allows the body to provide reliable protection from the outside world.

The epidermis in detail

These are the upper layers of the skin, which are the first obstacle to external influences. It is this protective layer that is called the epidermis. This ball consists of a stratified epithelium with a very specific structure. So, its upper layers consist of dead cells that form the stratum corneum, and living elements that carry out active division are located below.

As new cells appear, the old keratinized components are exfoliated and replaced. This is a simple biology called epidermal renewal. In addition to eliminating old cells, this process also involves the elimination of toxins, toxins accumulated in the lymph and blood.

They are absorbed by the cells and eliminated by exfoliation. Complete renewal of the epidermis (from the basement membrane to the stratum corneum) can last as long as 21 days (in young people) and up to 2-3 months.

This unique structure makes the layers of the epidermis impervious to water and its solutions. Accordingly, heat loss due to excessive humidification is avoided. At the same time, the membranes of epidermal cells contain a fairly large amount of fat. This allows cosmetics and drugs to penetrate through its layers and exert the necessary effect.

The structure of the epidermis suggests a complete absence of blood vessels. In this case, the nutrition of this layer is carried out at the cell-membrane level.

Modern biology has proven that the epidermis contains the same types of beneficial cells, depending on their functions:

Keratinocytes.
These are the elements that produce keratin. This function can be performed by different types of cells: spinous, basal, granular. Keratin is responsible for the elasticity and firmness of human skin.
Corneocytes.
These are transformed non-nuclear keratinocytes filled with keratin. They rise into the upper balls, become flat and perform a protective function, being a reliable barrier between the human body and the outside world.
Ceramides or ceramides.
These are specific fats that hold corneocytes together. They absorb moisture and fats.
Melanocytes.
These cells determine the shade of the human skin. They also provide partial protection from radiation and infrared radiation, preventing harmful sun rays from passing deeper.
Particles of Langergens.
They actively protect the body from the invasion of microbes and bacteria through the skin.

Modern biology has proven the importance of the epidermis, but the study of the cells of this layer is still just beginning.

Also, doctors distinguish 5 layers of the epidermis:

The importance of the epidermis is difficult to overestimate. After all, it is thanks to this layer that we are protected from external influences. Also, the appearance of human skin depends on the epidermis.

Derma and its features

This term refers to the inner layer of the skin. It is protected from the epidermis by a basement membrane. A table from the network or textbooks on biology, anatomy will help to study the structure of these layers in more detail. The average thickness of this part of the skin is no more than 0.5 - 5 mm.

This part of the human protective cover is characterized by the presence of hair follicles, blood and lymphatic vessels, as well as nerve endings, secretory glands and receptors. Accordingly, the dermis performs protective, bactericidal and thermoregulatory functions of the skin.

This part includes the following layers:

Reticulate.
It is a loose connective tissue with a high content of extracellular matrix. The latter includes collagen, elastin, reticulin, and polysaccharides. In fact, it is the skeleton of the human skin.
Papillary.
This layer contains specific "papillae" that create a special pattern of the skin, including fingerprints.

It is the layers of the dermis that form the external state of the epidermis, making the skin healthy or damaged.

Subcutaneous adipose tissue and its purpose

This part of the skin is also called the hypodermis. It performs thermoregulatory and protective functions. In fact, it is subcutaneous fat that softens falls and reduces the risk of damage to soft tissues and internal organs. It is located directly under the dermis and such features of the structure of the skin are very justified. After all, it is in the fatty tissue that the reserves of nutrients, including vitamins, are stored.

The thickness of this layer can be different. But don't think that less fat is better. Too thin a layer of fiber leads to rapid aging of the skin and the appearance of wrinkles, because it is this layer that serves as a support for the dermis and epidermis.

In adipose tissue, it produces estrogens - female hormones. Therefore, its increase is good for the fair sex and detrimental to men. Indeed, with an increase in the amount of estrogen in the blood, testosterone production automatically decreases, which leads to the development of sexual dysfunction and impotence.

Also, fatty tissue contains aromatase (the culprit in estrogen production) and leptin. The latter is responsible for appetite and the appearance of a feeling of fullness. This hormone is produced depending on the needs of the body. So, if the layer of subcutaneous adipose tissue is critically reduced, then the production of leptin increases. Therefore, you also need to listen to your body.

The skin is the largest human organ. It helps all living things to exist fully, stabilizing hormonal levels and protecting against a number of micro and macro dangers.

Leather I Skin (cutis)

The skin is involved in the processes of immunity. Distinguish between nonspecific, which does not depend on previous infections or vaccinations, which forms when the skin is exposed to UV radiation, and specific, which develops when agents penetrate into K., to which it is especially sensitive, for example, the causative agent of anthrax. The skin has low electrical conductivity, and its electrical resistance, especially of the stratum corneum, is high. Electrical resistance decreases in wet areas of K., especially with increased sweating, as well as in persons with a predominance of the tone of the parasympathetic nervous system. Electrical resistance depends on the physical properties of K., the functional state of the sebaceous and sweat glands, blood vessels of K., and the nervous and endocrine systems.

Through the skin (excluding K. of the head) secretes 7-9 G carbon dioxide and absorbs when t ° 30 ° 3-4 G oxygen, which accounts for about 2% of the total gas exchange in the body. Cutaneous respiration increases with an increase in ambient temperature, during physical work, an increase in barometric pressure, during digestion, acute inflammatory processes in the skin, etc. Cutaneous respiration is closely related to redox processes, the activity of sweat glands, rich in blood vessels and nerve fibers.

The absorption function is complex and not well understood. through K., water and dissolved salts in mammals practically does not occur due to the presence of shiny and stratum corneum impregnated with lipids. Fat-soluble substances are absorbed directly through the epidermis, and water-soluble substances are absorbed through the hair follicles and through the excretory ducts of the sweat glands during the period of inhibition of perspiration. Gaseous (for example, carbon dioxide) and some substances that dissolve and dissolve in them (chloroform, ether, etc.) are easily absorbed. Most toxic gases, except for skin blisters such as mustard gas, lewisite, do not penetrate through K.. Morphine, ethylene glycol monoethyl ether, dimethyl sulfoxide and other substances are easily absorbed, in small amounts.

The excretory function of K. is carried out by the sweat and sebaceous glands. The amount of substances secreted through K. depends on gender, age, topographic features of the skin (see Sweat glands , Sebaceous glands) . In case of insufficiency of the function of the kidneys or liver through K. of such substances, which are usually excreted in the urine (, bile pigments, etc.), increases. occurs synchronously in different parts of K. under the control of a c.s.s. Sweat contains organic matter (0.6%), chloride (0.5%), impurities of urea, choline, volatile fatty acids. On average, from 700 to 1300 are allocated per day ml sweat. sweat depends on the temperature of the environment, the state of K., the intensity of the basal metabolism, etc. Sweating increases with an increase in the temperature of the environment, dry air, hyperemia K.; during sleep or anesthesia, it sharply decreases and even stops. The sebaceous glands consist of 2/3 of water, and 1/3 of analogs of casein, cholesterol and some salts. With it, free fatty and unsaponifiable acids, metabolic products of sex hormones, etc. are released. The maximum sebaceous glands are observed from puberty to 20-25 years. The skin acts as a filter that prevents excess water from reaching the surface.

The pigment-forming function of K. is the production of melanin. This is produced by melanocytes, which contain specific cytoplasmic organelles - melanosomes, on the protein matrix of which melanin is synthesized from tyrosine under the action of tyrosinase. It is deposited as a melanoprotein complex. Melanogenesis is regulated by the melanocyte-stimulating hormone of the pituitary gland. the skin is mainly caused by the deposition of melanin. However, human K. contains other pigments - melanoid, oxyhemoglobin and reduced. Impaired pigmentation leads to hyperpigmentation (for example, in Addison's disease) or depigmentation (and others).

Among the nerve fibers innervating blood vessels K., adrenergic and cholinergic are distinguished. Neurohumoral factors constantly exert a regulatory influence on blood vessels. , norepinephrine and the posterior lobe of the pituitary gland cause vasoconstriction, while acetylcholine and androgens dilate them. Normally, most of K.'s blood vessels are in a semi-contracted state, the blood flow rate in the capillaries is insignificant; it varies greatly depending on local and general reasons. The dilated blood vessels of the dermis can accommodate up to 1 l blood (depositing role of the skin); their rapid expansion can lead to significant circulatory problems.

K. plays a very important role in thermoregulation of the organism. The production of heat energy in the body due to thermoregulation is maintained at a certain level despite fluctuations in ambient temperature (see Thermoregulation) . 80% occurs through K. by radiation, heat conduction, and due to the evaporation of sweat. Fatty lubrication of the surface of K. and poor thermal conductivity of the subcutaneous tissue prevent both excess heat or cold from the outside and excessive loss of heat.

Heat regulation is a complex reflex act in which the brain (thermoregulation centers) and sympathetic are involved; it is also influenced by the vasomotor and respiratory centers, sweating, adrenal glands, pituitary gland, thyroid and gonads. K.'s temperature depends on the time of day, food intake, the intensity of sweating and sebum secretion, muscle work and the age of a person. A person emits about 2,600 calories of heat per day, children are slightly more. K.'s temperature in different parts of it is not the same (from 31.1 to 36.2 °), the highest temperature in the skin folds is up to 37 ° in the norm.

The skin plays an important role in metabolic processes. In addition to gas exchange during cutaneous respiration, intermediate carbohydrate, protein, fatty, salt, and vitamin processes occur in K.. In terms of the intensity of water, mineral and carbon dioxide metabolism, K. is slightly inferior to the liver and muscles. To. Faster and easier than other organs, accumulates and gives up a large amount of water. Through K. water is released twice as much as through the lungs. Metabolic processes and acid-base balance depend on many factors, including on human nutrition (for example, when acidic food is abused in K., the sodium content decreases). To., Especially subcutaneous tissue, is a powerful depot of nutrient materials that are consumed by the body during fasting.

The skin is a huge receptor field through which the body's connection with the environment is carried out. She participates in various reflex reactions - to cold, high temperature, etc., as well as in the plantar, pilomotor and other reflexes. Exteroceptors K. perceive various external stimuli, which in the form of a nerve impulse are transmitted to the c.ns. There are different types of skin sensitivities. Pain occurs when exposed to mechanical, thermal stimuli and electric current, temperature - cold and thermal irritants. Tactile sensitivity (see Touch) is most pronounced on the pads of the fingers, in K. of the external genital organs, in the nipple area, where there is the greatest number of highly differentiated nerve endings. Its variant, obviously, is hair sensitivity K., which arises when touching the hair and depends on irritation of the complex basket-like nerve plexus of the hair follicle. Complex types of sensitivity include a sense of place (localization), stereognostic, two-dimensional spatial and a sense of separation (discriminatory sensitivity).

Different parts of K. do not perceive the same thing in the same way. It is believed that 1 cm 2 the skin has 100-200 pain points, 12-15 cold, 1-2 heat and about 25 pressure points. Most of the cutaneous receptors are polyvalent in function. Under the influence of various environmental factors, the number of functioning sensory receptors can change, It develops, especially to tactile and temperature irritations. the weakest to painful irritations.

Unconditioned and conditioned skin plays an important role in the life of the body. Newborns have congenital unconditioned skin reflexes - sucking and grasping. Distinguish between skin and skin reflexes (irritation and response occurs to K.), muscle-hair, unconditioned vasomotor - reflex Dermographism , vasomotor reactions in response to intradermal administration of adrenaline, histamine, etc. Musculocutaneous reactions include abdominal, cremaster reflex, plantar. There is also a galvanic skin reflex, a reflex to. The impulses coming from the skin receptors support normal muscles. Musculocutaneous reflexes are of great importance in human labor activity, especially in the automation of movements, the accuracy of which is developed as a result of the differentiation of skin and visual sensations, combined with proprioceptive ones coming from muscles and tendons. Painful irritations To. Are accompanied by a change in the secretion of the pituitary gland, an increased release of adrenaline, inhibition of the digestion process, a change in the biocurrents of the brain. There are also skin-respiratory, skin-vascular and other skin-visceral reflexes. Well-known reflex, which occurs not only at the sight of blood-sucking insects, but even at the mere mention of them, conditioned reflex (the so-called erythema of shame, anger), "goose bumps". The same conditioned reflex mechanism underlies hemorrhages, blisters, and even blisters caused by suggestion.

Structural proteins have been identified in the skin: reticulin, and keratin. concentrated mainly in the dermis, it makes up about 70% of the skin devoid of water and fat (see collagens) . Reticulin and elastin are contained in K. in much smaller quantities, they form the basis of reticulin and elastic fibers of the dermis, connective tissue membranes of the sebaceous and sweat glands, are part of the membrane of hair follicles. Keratin is the basis of the stratum corneum K. In its cells ends (the process of formation of the stratum corneum in the epidermis), which begins in the basal epidermal cells. The skin also contains protein breakdown products: uric acid, and creatinine, ammonia, etc. In the skin there are three times more of them (up to 150 mg%) than in the blood; especially a lot of them accumulate in pathologically altered areas of K. with the predominance of decay processes. The formation of the horny substance is regulated by genetic mechanisms, as well as by the endocrine and immune systems. Violations of keratinization () are observed in skin tumors, Daria's disease, etc. A significant part of K.'s cells, as well as other cells of the body (especially their nuclei), are nucleoproteins and (and RNA).

Of carbohydrates, K. contains glycogen and glycosaminoglycans. With the depolymerization of glycosaminoglycans (for example, with an increase in the activity of hyaluronidase), the gels formed by them decrease, and so on. K. rises for microorganisms and various toxic products, in K. it is formed and accumulates in mast cells; it plays an important role in the regulation of microcirculatory processes.

A variety of lipids are found in and on the skin. Neutrals make up the bulk of the subcutaneous tissue. They are dominated by the most low-melting triglyceride - triolein (up to 70%), in connection with which the human has the lowest melting point (15 °). On the surface of K., lipids mix and form.

The water content in Kazakhstan ranges from 62 to 71%. The skin is rich in enzymes, the most important of which are phosphorylase,. The mineral constituents of K. account for 0.7 to 1% of its dry weight, and in the subcutaneous tissue - about 0.5%. The skin is an important depot of sodium, potassium, calcium and other trace elements. For the normal state of K., zinc, arsenic, and some others, which are part of enzymes, vitamins, or play the role of activators of biological processes, are most important.

The skin is involved in the body's metabolism; it deposits blood, lymph, tissue metabolism products, macro- and microelements; due to the fact that proteins are temporarily delayed in K., their toxic effect on other organs is weakened. K. frees the body from excess water, toxic metabolites, which improves thermoregulation processes, increases barrier, bactericidal, and other functions. Separate stages of the chemical transformation of a number of substances that take part in metabolic processes occurring in other organs and tissues of the body take place in the skin. It forms sebum and.

Violation of protein metabolism leads to the development of gout (Gout) , Amyloidosis , Porphyrias , mucinosis of the skin (deposition of mucin in K.) and other diseases with pronounced changes in K. Violation of lipid metabolism is the cause of lipidosis (Lipidosis) . Changes in carbohydrate metabolism, accompanied by the accumulation of blood and K., lead to necrobiosis lipoid (necrobiosis lipoid) , contribute to the occurrence of furunculosis (see Furuncle , chronic pyoderma and other diseases K. Deviations and activity of enzymes are noted in dermatoses, for example, eczema (Eczema) , Neurodermatitis , Psoriasis .

Metabolism in K. is influenced by nervous and hormonal factors. Dysregulation of biochemical processes at the cellular and intracellular levels play an important role in the occurrence of skin diseases. In particular, an important pathogenetic mechanism of psoriasis is a violation of the cellular regulatory system adenylcyclase - cyclic.

Lack of vitamin A plays a role in the development of Ichthyosis a , seborrhea (seborrhea) , Defeat the disease (Defeat the disease) , dystrophy of nails (see. Nails), etc. Lack of vitamin PP causes the development of pellagra (Pellagra) with severe skin lesions, and vitamin C - scurvy (scurvy) . The pathogenesis of neurodermatitis is associated with a lack of B vitamins, especially B 6. In the pathogenesis of some skin diseases, violations of water and mineral metabolism are important. Shifts in acid-base balance affect the bactericidal functions of the skin. In adults, the pH of the skin surface is 3.8-5.6: in women, this indicator is slightly higher than in men. In the armpits, inguinal-femoral folds, sweat has a slightly alkaline or slightly acidic reaction (pH 6.1-7.2). Pronounced shifts in pH towards an alkaline reaction contribute to the occurrence of mycoses (Mycoses) . In addition to the biochemical processes common to the body, transformations inherent only to it occur in K.: the formation of keratin, melanin, sebum, and sweat.

With slowly developing acidosis, intercellular edema occurs (), manifested by multi-chambered vesicles (see Rashes) . When intercellular communication is disturbed, unicameral intraepidermal bubbles are formed. Coagulation and collisional cell death (see Necrosis) leads to erosion that heals without a scar or ulcer (Ulcer) , penetrating into the connective tissue part of K. and healing with the formation of a scar.

Often K.'s inflammation is accompanied by the development of purulent exudate and the formation of pustules (see. Rashes) . With productive inflammation, a cellular one with a dermal papule or tubercle is formed (with specific inflammation). , resolving without necrosis, ends with cicatricial atrophy, and disintegrating - with a scar. Chronic granulomas constitute a special group of inflammatory processes. Inflammatory infiltrate in the dermis, disrupting, causes the appearance of various secondary changes in the epidermis (edema, atrophy, etc.). Inflammation of the subcutaneous tissue is manifested by edema, the formation of a node or diffuse infiltrate. Inflammation To. Can occur as a result of hypersensitivity to a strictly defined antigen (see.Allergy) , in other cases it is not specific and is caused by any strong stimulus.

K.'s condition is associated with the condition of the whole organism. Nephropathies are often accompanied by the so-called cutaneous uremia caused by azotemia, oxalemia, and urea retention. Focuses of chronic infection (in the tonsils, teeth, etc.) can be the cause of a number of dermatoses. Often a backdrop for the onset and development of eczema, urticaria (urticaria) , neurodermatitis, circular hair loss are neurovegetative disorders. After mental trauma, red flat, psoriasis, etc. often appear. The skin reacts to disruption of the endocrine system. So, a disorder of the thyroid gland function contributes to the development of myxedema of the skin, increased sweating, itching, urticaria, eczema, etc.; dysfunction of the ovaries - chloasma (see Dyschromia of the skin) ; adrenal gland disease - hirsutism (see Viril syndrome) , increased pigmentation; diseases of the pancreas are accompanied by persistent furunculosis, etc.

Certain (for example,) atmospheric factors (long-term, wind, cold, etc.), mechanical, physical, and chemical influences can have an adverse effect on K.. Stagnation in the circulatory system contributes to the occurrence of varicose ulcers, etc.

A variety of factors affecting K., the complexity of its morphological structure and a wide range of functions performed determine a large number of skin diseases (about 2 thousand different forms), the classification of which has not been finally developed (see Dermatoses) .

A large group is made up of K.'s lesions associated with hereditary factors (see Genodermatoses) or which are congenital malformations of the fetus as a result of adverse effects in the processes of embryogenesis (intrauterine intoxication, infections, circulatory disorders, etc.) K., due to genetic factors, are very diverse ; often they wear a family one. Congenital malformations and developmental anomalies not associated with genetic factors are more rare. Part of malformations To. Are abortive manifestations of more complex congenital defects: swimming membranes - an abortive form of syndactyly (see Brush) , sacral hypertrichosis is a latent manifestation, congenital sinuses and cysts on the neck and face are the result of incomplete closure of congenital fissures, additional breast nipples are incomplete gynecomastia, etc.

With other congenital anomalies of K., the main disturbances in the development of the fetus are concentrated in K. Thus, the congenital absence is known - K., accompanied by the underdevelopment of K.'s appendages and teeth (congenital ectodermal). Congenital aplasia of the skin (defect of the epidermis and dermis) is characterized by the presence of ulcers in the child at birth up to 10 cm in the parietal, occipital or posterior auricular region of the head. Congenital defect K. is formed in the fetus in the form of a bullous lesion (bladder), by the time the child is born, it forms in the place of the bladder. Gradually, it closes, leaving behind a cicatricial atrophy. Congenital aplasia K. can be combined with a defect of the bones of the skull. With other types of aplasia K., areas devoid of skin can be located on the body, limbs. They are covered with a thin membrane through which the underlying organs and tissues are clearly visible.

Such congenital anomalies as rubber hyperelastic K., imperfect desmogenesis, pachyderma are associated with changes in connective tissue. The number of developmental defects includes birthmarks, angiomas, lymphangiomas, varied in clinical forms.

A large group is made up of diseases caused by damage to K. - mechanical (for example, abrasion, callousness , Intertrigo) , beam, incl. ionizing radiation (see Dermatitis , Photodermatosis) , exposure to electric current, high and low temperatures (see Burns , Frostbite) , as well as various chemical and biological factors.

Inflammatory lesions of K. may be based on allergic reactions of the body, changes in the nervous and endocrine systems (see.Toxidermy , Hives , Eczema , Neurodermatitis , Pruritus, etc.). Skin is often affected by diffuse connective tissue disorders (see table Diffuse Connective Tissue Disorders) , Sarcoidosis , vasculitis of the skin (vasculitis of the skin) , metabolic disorders in the body (see Lipidosis , Amyloidosis , Calcification , Xanthomatosis, etc.).

Pathological processes in K., associated mainly with individual morphological structures of the skin, - see Hair , Nails , Sweat glands , Sebaceous glands .

Skin tumors... According to the WHO histological classification (1980), among tumors K. distinguish between skin, benign, precancerous (precancerous) skin diseases, tumors with local growth and malignant tumors. By origin, epithelial, pigment and connective tissue tumors of the skin are isolated.

Malformations of the skin. These include papillomatous, comedogenic nevus, epidermal cyst, hair cyst, dermoid cyst (see Dermoid) , whiteheads, atheroma, etc.

Papillomatous malformation is characterized by the appearance of warty papillomatous growths (hyperkeratotic nevus) from the moment of birth or in early childhood in any area of K. A limited form is distinguished in the form of a dense grayish-brown focus and a multiple form, in which the lesions may tend to orderly localization (along the Zakharyin-Ged zones). often combined with other skin malformations (pigmented nevus, nevus of the sebaceous glands).

Comedonic nevus is localized mainly on the limbs and trunk. It is within which follicular papules are closely grouped. The central part of the papules is penetrated with dark gray or black horny masses (preserved after their removal).

Seborrheic keratosis, or seborrheic, occurs more often in the elderly (after 40 years); localized in closed areas of the skin, for example, the trunk ( rice. 3 ). It is characterized by the appearance of sharply hyperpigmented (from brown to black) plaques, often multiple, with a diameter of 0.5-4 cm and more, covered with easily removable greasy crusts.

Benign epithelial tumors can originate from sweat glands, hair follicles, and sebaceous glands. Benign tumors of the sweat glands are papillary, eccrine pore, papillary, eccrine spiradenoma, etc.

Papillary hydradenoma is a solitary mobile tumor of the apocrine gland. It is found mainly in women, localized in K. of the external genital organs, as well as in the perineum. Has a soft texture and large size (4-6 cm). Usually grows slowly.

Eccrine poroma is a tumor of the intradermal duct of the eccrine sweat gland. It is localized mainly on the plantar surface of the feet, on the palms, the inner surface of the fingers. It is a single flattened tumor formation in the form of a plaque with a diameter of 10-20 mm with a smooth or hyperkeratotic surface of pink or dark brown color. Eccrine poroma is painless on palpation; may ulcerate.

Papillary syringocystadenoma () - excretory duct of the sweat gland. It is, as a rule, a nevoid formation. It is rare, usually in children and adolescents. It is located more often on the scalp, neck, groin and axillary folds. It looks like a single or multiple tumor-like formations of dense consistency, grayish or grayish-yellow in color with papillomatous growths on the surface.

Eccrine spiradenoma is a tumor that develops from the glomerular part of the sweat glands. It is rare, more often observed in young men. It is localized, as a rule, on K. of the face, the front surface of the body. It is a dark yellow or bluish-red color, dense consistency, sometimes painful on palpation.

Benign epithelial tumors of the hair follicle include cylindroma, trichoepithelioma, etc., localized on the face and scalp (the so-called turban tumor). It is a large tumor with a smooth surface ( rice. 4 ), characterized by progressive growth, a tendency to relapse after surgical excision.

Trichoepithelioma is multiple and single. The plural form is more common in childhood - hereditary. Numerous small nodules are located mainly on the face ( rice. 5 ), sometimes the scalp, neck, front surface of the body. The solitary form occurs mainly in adults - actually trichoepithelioma. It is localized on any part of the body, usually on the face.

A benign tumor is a true adenoma of the sebaceous glands. It is very rare, mainly in old age. It looks like single, dense, round, sometimes nodules or knots sitting on a leg.

Fibroma can appear on any part of K. Distinguish between hard and soft fibroids. Hard fibroma has a wide base, dense texture, smooth surface, normal skin color or slightly pinkish. This is a limitedly mobile tumor that rises above the surface of K. Soft fibroma is multiple and single. It is localized mainly on the neck, the front surface of the chest, in the groin folds and armpits. It looks like a bag-shaped hanging tumor of various sizes with a wrinkled surface of pinkish or brown color.

Dermatofibroma can be single ( rice. 6 ) and plural. It is found, as a rule, in women, on K. of the upper and lower extremities. dense consistency, dark brown, round shape deeply located in K. often does not protrude above its surface.

A bulging dermatofibrosarcoma is a locally invasive tumor. It occurs more often in men in the area of the shoulder girdle, on the head. It can be single and multiple. protrudes above the surface of K., has a smooth, bumpy surface that can ulcerate. Characterized by a slow and a tendency to develop relapses after excision.

Hemangioma develops from blood vessels. Allocate capillary ( rice. 7 ), arterial, arteriovenous and cavernous ( rice. eight ) forms (see. Blood vessels , tumors). A special form of hemangioma is pyogenic granuloma ( rice. nine ). It arises as a result, is localized on the face, more often in the area of the lips, on the upper limbs. It is a dark red tumor on a pedicle or broad base with an erosive surface.

Lymphangioma is a tumor arising from the lymphatic vessels. It is often detected from birth. It is localized on any part of the skin. Combines with hemangioma. Distinguish between capillary, cystic and cavernous forms. Against the background of cystic and cavernous lymphangiomas, areas of papillomatosis and hyperkeratosis may develop. Secondary lymphangioma can be a manifestation of lymphostasis, sometimes appears after an infectious disease (for example, erysipelas).

Leiomyoma is a tumor arising from the muscles that lift the hair. There are 3 clinical types: multiple leiomyoma, solitary leiomyoma on the genitals and nipples, and angioleiomyoma, which develops from small blood vessels K. Multiple leiomyoma is characterized by the appearance of small tumors on the trunk and limbs (3-5 mm in diameter) round in shape, with a smooth surface, painful on palpation, with a tendency to grouping. Solitary leiomyoma has a size of up to 20 mm in diameter; erythema is observed around the lesion. - solitary tumor of deep red color, dense elastic consistency. It is often localized in the area of large joints.

Lipoma - tumor of adipose tissue in the form of single or multiple foci. Localized in any part of K., towering above its surface. Has, as a rule, large sizes (up to 10 cm in diameter), doughy consistency, normal skin color. A variant of the lipoma is symmetrical multiple (Derkuma), characterized by the appearance mainly on the upper extremities of lesions that are painful on palpation.

Various forms of a pigmented nevus and belong to benign pigmentary tumors K. Pigmented nevi are characterized by the appearance on K. of spots or neoplasms consisting of nevus cells. They appear after birth or in the first years of life; sometimes appear in adolescence and middle age under the influence of sunlight or during pregnancy. Pigmented nevi - spots or flat nodules of dark gray, brown or black color, elongated or rounded, 1 in diameter cm and more ( rice. ten ). The surface of the pigmented nevus is often smooth, but sometimes there are papillary warty growths. In some cases, a large nevus occupies a significant part of the body, face, neck, or extremities and represents a cosmetic defect (giant pigmented nevus). Hair often grows on its surface. Sometimes the nevus is blue - a blue nevus. It is more common in women on the face and forearms. A variety of blue nevus is Mongolian. It occurs mainly in persons of Asian descent 1–2 days after birth, usually in the lumbosacral region. Has a bluish or brownish color, up to 10 cm and more. After 4-5 years, the stain gradually fades and disappears.

Ota's nevus is more often observed in women - representatives of Asian peoples. It can be congenital or appears in the first years of life. It looks like a pigment spot located on the face along the I and II branches of the trigeminal nerve (, the zygomatic region, the wings of the nose, as well as the sclera and eyes). Sutton's nevus (Sutton's disease) is also distinguished - a small pigment spot with a rim of depigmented skin, localized on the trunk or extremities.

Blue nevus, Oty's nevus, pigmented nevus with papillary warty growths during trauma can transform into melanoma.

Pre-malignant skin diseases. These include pigmented xeroderma (pigmented xeroderma) , radiation damage to the skin (see radiation damage) , solar keratosis, etc. A number of authors include in this group also Bowen's disease, Keir's disease and Paget's disease (when localized outside the nipple and areola of the mammary gland), which are rare.

Solar keratosis occurs as a result of excessive sun exposure. At the same time, against the background of poikiloderma (a combination of foci of hyperpigmentation with areas of atrophy), multiple foci of hyperkeratosis appear in the form of elongated or oval plaques up to 0.5-1 cm in diameter, covered with dense gray scales. Bowen's disease or squamous cell carcinoma may develop in the affected areas.

Bowen's disease is considered by most researchers as intraepidermal cancer. It is observed mainly in persons of middle and elderly age, more often it is localized on K. of the face, trunk. Usually it is a single grayish-brown plaque, poorly infiltrated, with irregular, clear boundaries, covered with scales or crusts.

The lesion slowly grows along the periphery, its surface often ulcerates, there are areas of atrophy on it, which, together with scales and cortical layers, gives the tumor a motley appearance. People with Bowen's disease are often diagnosed with cancer of the internal organs.

Paget's disease when localized outside the nipple and areas of the mammary gland is characterized by limited foci of maceration and oozing, located mainly in the perineum and navel.

Tumors with localized growth. An epithelial tumor with local growth is (basal cell carcinoma). It develops from the basal layer of the epidermis or K.'s appendages (sebaceous and sweat glands). This is the most common epithelial tumor K. It is observed mainly in old age. Characterized by invasive growth; extremely rarely metastasizes. Clinical manifestations are diverse. Allocate superficial (the most favorable form), cystic, ulcerative, scleroderma-like and pigmented forms of basal cell carcinoma.

Superficial basalioma is a limited spot, along the periphery of which there is a ridge, consisting of separate nodules ("pearls"). It is localized more often in open areas of the body exposed to insolation, prolonged mechanical irritation. In persons with fair skin, multiple lesions may occur, which merge into large plaques covered with scales ( rice. 12 ). Often, spontaneous growth occurs in the center of the plaque, and tumor growth along the periphery (self-scarring basalioma).

With cystic basalioma, the lesion is often single, sharply demarcated from the surrounding tissue, bright pink, pasty consistency; there are often telangiectasias on the surface. It is localized mainly on the skin of the face (around the eyes, nose).

Ulcerative basalioma ( rice. 13.14 ) can develop from superficial or cystic. It occurs more often on the chin, at the base of the nose, or in the inner corner of the eye. Manifested by the formation of nodules prone to ulceration. It is characterized by tumor infiltration of the underlying tissues with the development of a defect up to the destruction of bone and cartilage tissue. The most severe forms of ulcerative basalioma are - a corrosive ulcer ( rice. 15 ) and ulcus terebrans (penetrating ulcer). In ulcus terebrans, the process extends to the periphery. In some cases, papillomatous growths (verrucous-ulcerative basalioma) appear on the ulcerated surface.

With scleroderma-like basalioma on the face, upper body, plaques of dense consistency with clear boundaries are formed. They resemble foci of scleroderma, in which an erythematous corolla is noted along the periphery of the lesion. Unlike scleroderma, with scleroderma-like basalioma, a ridge-shaped edge and single nodules - "pearls" are found along the periphery of the lesion.

Pigmented basalioma has a darker color (from yellowish-brown or bluish-brown to dark brown or black), which is associated with the presence of melanin in the cytoplasm of tumor cells.

Depending on the histological picture, multicentric, solid and adenoid forms of basalioma are distinguished. A logical connection between the histological picture and the clinical form of basal cell carcinoma, as a rule, is not observed. In those cases when structures resembling histologically reveal, they speak of trichobasalioma. It is localized on K. of the forehead, scalp in the form of a single, less often multiple nodules of a rounded shape from 2 to 5 mm in diameter, dense consistency, dark gray or brownish color. In rare cases, the nodules are larger, have an uneven surface, sometimes with pronounced telangiectasias.

To malignant skin tumors include squamous cell carcinoma, pigmented tumors - precancerous Dubreya and melanoma (Melanoma) . Squamous cell carcinoma K. is an epithelial malignant tumor. It occurs more often in places of constant irritation, mechanical, against the background of long-term non-healing trophic ulcers, fistulas, radiation damage K., and can also develop from lesions characteristic of Bowen's disease, pigmented xeroderma, solar keratosis. According to the clinical picture, endophytic (ulcerative) and exophytic (tumor or papillary) forms of squamous cell carcinoma are distinguished. In the ulcerative form, a crater-shaped ulcer with a dense bottom and roller-like edges is formed. slowly but steadily growing, bleeding. In the papillary form, single hard nodules look like a wart or keratoacanthoma, merge together into large lesions resembling cauliflower ( rice. 16 ). Keratinizing squamous cell carcinoma is characterized by infiltrative growth into the underlying tissues, metastases to the lymph nodes and lymphatic vessels, and in advanced cases, to the blood vessels.

Dubreus' precancerous melanosis is a slow-growing tumor that usually occurs after age 30, more often in women. It is localized, as a rule, in open areas K. It has the appearance of a single large plaque (40-60 mm in diameter) with uneven outlines and uneven pigmentation (from light brown to dark brown and black). A tendency to growth, a change in the color of the tumor (darkens), the development of papillomatous growths on the surface or the appearance of areas of atrophy indicate its transformation into melanoma.

Treatment. Most of K.'s tumors are not accompanied by noticeable subjective sensations. When neoplasms appear, the patient should be referred for a consultation with an oncologist or dermatologist (oncologist), who establishes on the basis of anamnesis data, clinical signs and results of histological and cytological examinations and conducts. With benign tumors K., surgical treatment (removal of the tumor) is carried out in the case of localization of the tumor in places subject to injury, as well as at the request of the patient (for example, with a cosmetic defect). Pre-malignant diseases are subject to compulsory treatment. For this purpose, a surgical procedure is used, incl. electrosurgical, cryodestruction, radiation therapy (Radiation therapy) , laser (see Lasers) . According to indications, various cytostatic drugs are also locally prescribed (5-fluorouracil, flutorafur, prospidin, etc.).

Prophylaxis consists in the early detection of the initial signs of a tumor K., conducting preventive examinations and identifying risk groups (persons suffering from long-term non-healing ulcers, with cicatricial changes in the skin, etc.), in the active treatment of precancerous dermatoses. Excessive sun exposure and contact with oncogenic substances should be avoided.

Bibliography: Apatenko A.K. Epithelial tumors and skin malformations, M., 1973; Berenbein B.A. Skin pseudo-cancer, M., 1980; Differential Skin Diseases, ed. B.A. Berenbein and A.A. Studnitsina, s. 366, M., 1989; Kalantaevskaya K.A. and physiology of human skin. Kiev, 1972; P.V. Kozhevnikov General, L., 1970; Guidelines for the pathological diagnosis of human tumors, ed. ON. Kraevsky and A.V. Smolyannikov, s. 403, M, 1976, bibliogr .; Trapeznikov N.N. etc. Pigmented nevi and skin neoplasms, M., 1976, bibliogr.

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

The node in the region of the lower part of the auricle "> of the patient can contribute to the fact that the course of the developing lesion K. will weaken or even be suspended. By taking a number of precautions, it is possible to prevent the spread of a number of infectious skin diseases even before going to the doctor.

In infants, exudative-catarrhal occurs, manifested in the hereditary tendency of the child's body to inflammatory processes, allergic reactions. The first signs of such a diathesis may be in the nature of a milk crust, persistent diaper rash of the skin, the so-called geographical language.

Milk scab manifests itself in the form of yellowish scale-crusts, which sit quite tightly on the skin of the scalp of the child, especially in the parietal region. In these cases, a nursing mother needs to carefully analyze her diet and exclude foods that have an allergenic effect from it (see below). On the crusts, apply warm boiled vegetable oil (sunflower, olive, peach) for several hours, then gently comb the softened crusts with a comb and then wash your hair; repeat the procedure if necessary.

With excessively tight swaddling of the child, overheating it, insufficient care of the skin (especially in the axillary, inguinal-femoral, intergluteal folds), as a result of the irritating action of the products of skin secretion (fat, sweat), as well as urine, feces, the skin turns red, macerates - diaper rash occurs. To prevent the further development of this process, it is necessary to make adjustments to the child care system, make sure that it does not overheat, change linen frequently, boil it, iron it. An important role is played by careful observance of the toilet of the genitals and perineum: after each urination and bowel movement, the skin should be washed with a weakly borne solution of potassium permanganate or a decoction of chamomile, oak bark, St. John's wort, or a string, diluted in boiled water to a slightly yellow color. Skin folds should be treated with sterile oil (olive, peach, sunflower, rosehip, sea buckthorn), fish oil, calcium liniment or baby cream. You can also use talcum powder. It is advisable to leave the affected areas of the body open more often. Persistent diaper rash can be a sign of exudative diathesis, and therefore should be reviewed by the nursing mother (see below). In the presence of erosions and abrasions in the diaper rash area, it easily joins, in this case, the child should be shown to the doctor.

In conditions of improper child care (excessive, insufficient fluid intake) in children who are weakened, suffering from rickets, feverish, as a result of imperfect thermoregulation system and increased sweating, small (punctate) pink nodules and vesicles often appear on the skin of the back, the back of the neck, buttocks - prickly heat... In this case, daily hygiene with the addition of a decoction of chamomile is advisable. After washing, the skin is gently blotted with a soft, carefully ironed diaper or towel. The child's skin should be wiped daily with a warm alcohol solution (half vodka with boiled water). You should also drink plenty of water for the child, take care of his more comfortable clothes, stop excessive wrapping, use air baths, avoid using oilcloth or plastic wrap in the form of linings under the sheet during prolonged sleep, which will help avoid overheating and sweating.

Since children's skin is tender, the slightest injury and pollution can lead to the appearance pustules- small red nodules with a purulent head at the top or vesicles with yellowish purulent contents. When such skin changes appear, you should refrain from bathing the child, treat, if they are single, with a solution of brilliant green (brilliant green), fucorcin or gentian violet, and wipe the skin around them with a warm alcohol solution (vodka in half with boiled water). At the same time, it is very important to change the linen frequently, which must be boiled and thoroughly ironed. If there are many rashes or they continue to appear, you should consult a dermatologist or pediatrician.

Skin allergies. In case of violation of the diet by a nursing mother (consumption of oranges, chocolate, honey, condensed milk, etc.), with the introduction of complementary foods or the transition to artificial feeding in infants, manifestations of exudative diathesis may occur in the form of skin redness, bright red small nodules, bubbles, with opening of which weeping skin areas are formed. After a while, they become covered with yellowish scales, crusts. Most often, such skin changes occur on the face (especially on the cheeks), buttocks, the back of the hands, forearms, feet, legs, thighs and are accompanied by itching. These skin changes can progress to childhood eczema and other difficult-to-treat allergic skin conditions. By combing the affected skin, the child will be able to introduce infectious agents into the lesions, as a result of which the process will worsen. The development of exudative diathesis is promoted by age-related immaturity of the digestive system, insufficient secretory activity, and sometimes enzyme deficiency, as a result of which a number of food products can cause an allergic reaction in such children in the form of skin lesions. It should be borne in mind that the leading food allergens for children can most often be cow's milk, especially its protein lactoglobulin (boiling milk causes the destruction of lactoglobulin, and milk becomes less allergenic); chicken eggs, especially protein (heat treatment reduces their allergic properties, but does not completely destroy); fish, caviar, crayfish, crabs, shrimp and products from them (heat treatment has little effect on the degree of allergic reaction to these products); grain products (usually wheat, rye,); fruits and (most often oranges, tangerines, lemons, strawberries, strawberries, tomatoes, carrots); and nuts; honey, chocolate, coffee, cocoa.

The spread of artificial feeding, the early introduction of mixtures made from cow's milk, often leads to a rapid increase in sensitivity to food allergens. In this case, it can be combined with medicinal, household (home, fluff, animal hair), pollen (pollen of herbs, flowering trees). If the child has a pronounced taste for milk, then you can try to use it in his diet (kefir, yogurt, biolact, etc.). Acidophilic products prepared by fermenting dairy products, including dry ones, with special acidophilic lactobacilli with proteolytic (protein-degrading) and antibacterial properties are also advisable. You can enter fruit, vegetable purees and beef meat at an earlier date, and cook porridge in fruit and vegetable broths. Foods are often steamed to reduce the content of extractives.

Potatoes, white cabbage, lettuce, peeled cucumbers, green onions, green apple puree, plums, dried fruits, rose hips, beef, cottage cheese. You cannot give such children meat, chicken, fish broths, tomatoes, citrus fruits, cauliflower, green peas, spinach. In older children, you need to be very careful with the introduction of chicken, eggs, into the diet. With good tolerance, you can give boiled chicken meat (without skin and chicken broth), hard-boiled chicken eggs once a week.

Proper nutrition will in many cases prevent the development of chronic allergic diseases. At the same time, in the diet, it is necessary to provide for the intake of proteins, fats and carbohydrates, trace elements, vitamins into the body, since this is a condition for the normal functioning of the body and, in particular, its immune system, which plays an important role in the development of allergic reactions.

The indispensable components of food are protein products, the lack of which in a child can lead to growth retardation, metabolic disorders, unfavorable changes in the function of the liver, pancreas, etc. The participation of proteins in the formation of the body's defense mechanisms (immunity) is very important. and vitamins promote the synthesis of hormones, enzymes. At the same time, easily absorbed fats, which enter the body in large quantities, slow down the synthesis of protective antibodies, increase the tendency of tissues to inflammatory reactions, and enhance sensitization processes.

Among the foods that should be avoided by both children and adults with the appearance of an allergic rash on the skin are eggs, canned food, citrus fruits, mushrooms, smoked and fatty sausages, crabs, strawberries, chocolate and honey.

Adults should adhere to a predominantly dairy-vegetable diet with a reduced content of table salt, with the exception of spicy, smoked, salty foods, and alcohol. The diet may contain boiled meat, fish, mainly river (low-fat), cottage cheese, kefir and other lactic acid products, buckwheat, rice and oatmeal, vegetarian soups, vegetables, fruits.

Of all the organs of the human body, the largest is the skin. Here are 10 interesting facts about our skin.

Square

People have different heights, fullness, respectively, and the skin area of different people will differ, but on average this figure is at the level of 1.5-2.5 m2. The weight of the multi-layered skin is over 11-15 percent of a person's weight.

The area of the skin in an adult reaches 1.5-2.5 m?

Thickness

In an infant, the thickness of the skin is one millimeter. With growing up, it remains thin only on the eyelids. In an adult, the average value of the skin thickness increases several times. The palms of the hands and feet are the places with the thickest skin.

The palms of the hands and feet are the places with the thickest skin.

Update

This separate organ has its own specific functions; the number of skin cells in the body is from 300 to 350 million. The body must produce more than 2 billion skin cells per year. The fact is that in a year, all skin cells change at least 6 times (complete replacement - in 55-80 days). The process of completing the cell cycle occurs at a rate of 0.6 million horny scales / hour (this amount corresponds to a weight of 0.7-0.8 kg).

Human skin at high magnification. Horny scales are clearly visible.

Complex structure

The skin has a complex structure, it contains different types of cells. In addition, the largest human organ contains glands (sebaceous and sweat), capillaries and hair. In a square centimeter of skin, there are about 230-250 glands (200 sweat, 30-50 sebaceous), two meters of capillaries and two dozen hairs.

Sweating ability

A person sweats and this is very good for his body. Sweat on the surface of the skin helps to cool it. The work of the kidneys is facilitated, due to the work of the sweat glands, the body gets rid of excess moisture and harmful products that arise during the digestion of food during metabolism. In the heat, several liters of sweat (3 or more) can be released through the pores of the skin surface.

In hot weather, several liters of sweat may be released through the pores of the skin surface.

Vitamin D synthesis

When certain conditions are created, the skin can serve as a synthesizer of useful substances. For example, when the sun's rays hit the skin, complex processes occur that promote the synthesis of vitamin D. From this point of view, tanning is useful, but one should not forget about the properties of ultraviolet rays that are destructive for all living cells. In a solarium and in the sun, tanning of the skin should be taken in moderation and in a certain mode recommended by doctors.

When sunlight hits the skin, complex processes occur that promote the synthesis of vitamin D

Multifunctionality

Among the main functions assigned to the skin by nature, the following can be noted:

protective function from overheating of the body and mechanical damage, from radiation, including the ultraviolet part of the light spectrum, from microbes and harmful substances;
the function of regulation through the mechanism of sweating of equilibrium in the amount of water, the presence of certain substances;
through the skin, the body and the external environment exchange the necessary substances, the skin is to some extent an auxiliary respiratory organ;
tactile function: receptors are built into the skin, due to which a person has a sense of touch;
function of an appearance shaper: the features of the facial skin and subcutaneous mimic muscles allow you to visually distinguish one person from another and convey your emotions.

The mimic properties of the skin allow us to communicate our emotions to each other.

Water resistance

The waterproofness of the skin is ensured by its outer layer, the epidermis. Its cells are in very close contact with each other and have a layer of fat on the outer surface. If the body is in water for a long time, the extracellular layer of fat becomes thinner and water gains access to the skin cells, as a result it swells.

Shriveled skin from prolonged exposure to water

Cleanliness and excessive sterility

On the surface of the skin, there are colonies of beneficial microorganisms that help in the fight against pathogenic bacteria. If you achieve absolute sterility, you can weaken the protection: excessive sterility is harmful to the skin.

Bacteria on the skin under a microscope

First cells and dust

During his life, each person loses up to hundreds of kilograms of horny scales, which turn into dust. In the air of your home (office) or apartment, when the sun's ray penetrates, you can clearly see a huge amount of the smallest dust. Almost 2/3 of this dust consists of skin horny scales. Billions of tons of dust grains of the same composition are absorbed by the atmosphere of the planet.

Almost 2/3 of this dust in your room consists of horny skin scales.

Sincerely,

The skin protects the body of humans and animals, it is a barrier between the body and the external environment. It has a complex structure and various functions. It forms a separate organ with its own blood supply, inherent innervation. The area of the skin of an adult is about 2 square meters and depends primarily on the height and body weight.

Skin weight is equal to 15% of human body weight.

Skin thickness varies on different parts of the body. The skin can have a thickness of 0.5 to 5 mm. On its surface there is a specific pattern of triangles and rhombuses forming a grid. It is especially visible on fingers, palms, soles.

Human skin is only 70% water, it is denser than many other organs. In this article, we will tell you how the human skin works, what are its functions.

How the skin works

The skin has a layered structure. It includes:

epidermis;
the skin itself, or dermis;
hypodermis (adipose tissue).

The epidermis is the uppermost cover, it is represented by several layers of epithelial cells. The cells of the lower layer of the epidermis are constantly dividing, ensuring rapid recovery and renewal of the skin. The closer the cells are to the surface, the less they multiply and the more keratin and other dense proteins they contain. On the surface of the epidermis, keratinized cells are located, which are permanent. This is how the skin is constantly renewed.

The epidermis of an adult is completely renewed in two months, a baby - in three days.

The upper, stratum corneum of the epidermis protects the skin from damage. It is thickest on the soles and palms. The thinnest epidermis is located on the eyelids and the skin of the male external genital organs.

The epidermis does not allow cosmetics based on collagen and elastin to pass through itself due to the too large size of these molecules.

The dermis is the middle layer of the skin, which is made up of connective tissue. It includes thin bundles of elastic tissue, collagen, muscle fibers. Nerve endings are located in the dermis. The same layer contains a large number of arteries, veins and lymphatic capillaries that feed not only this layer itself, but also the epidermis, devoid of blood vessels.

The vessels of the skin are able to accommodate a third of the entire blood of the body.

The hypodermis is represented by a network of fibers, between which there are fat cells. It helps protect the organs under the skin from damage. The thickness of the fatty tissue is different: on the scalp it is 2 mm, and, for example, on the buttocks it reaches 10 cm. There are many vessels and nerves in the fatty tissue. Sweat glands and hair follicles are also located here. In the mouth of the hair follicles, the ducts of the sebaceous glands open.

Skin, nails and hair are almost completely formed by the 7th month of intrauterine development.

Function of the skin

Protective

The skin protects the underlying tissues from bruises, pressure, stretching. The epidermis does not release the tissues.

In addition, it prevents various chemicals from the external environment from entering the body. contained in the skin absorbs ultraviolet radiation from the sun. The skin has antimicrobial properties. The epidermis is impervious to many pathogens. Sweat and sebum create an acidic environment in which many germs are killed.

On the surface of the skin there are also beneficial microbes that protect it from pathogenic bacteria, therefore, the absolute sterility of the skin is harmful.

Thermoregulatory

The skin is actively involved in heat transfer. If the external environment has a high temperature, the vessels of the skin expand, enhancing heat transfer. At the same time, heat is lost with sweat. At a low temperature of the environment, the vessels of the skin spasm, preventing heat loss. Thermoreceptors - sensitive "temperature sensors" located in the skin, are involved in the regulation of this process.

In a day, under normal conditions, a person loses up to a liter of sweat, in the heat this amount can reach 5 - 10 liters.

Excretory

With sweat, excess salts, some toxins, and also medicinal substances are released through the skin.
Urea, uric acid, acetone, bile pigments and other metabolic products pass through the skin. These processes are especially noticeable in diseases of the kidneys and liver, which normally remove these toxins with urine and bile. At the same time, an unpleasant odor begins to emanate from the patient's skin, which helps doctors in diagnosis.

Receptor

The epidermis contains tactile cells. Their superficial location leads to high tactile sensitivity. Special nerve formations provide sensitivity to cold, heat, position in space, pressure and vibration. Pain, burning sensation and perceived free nerve endings located in the upper layer of the skin.

Thermoreceptors perceive temperature in the range of +20 - + 50˚С; at lower and higher temperatures, the impact is most often perceived as pain. A person feels cold much better than warm.

Regulatory

The skin is responsible for the synthesis and accumulation of vitamin D and some hormones.

Vitamin D can be formed only on the surface of the skin, from which the sebum layer is not washed off, and it should not be tanned.

Immune

Langerhans cells (tissue macrophages), which are able to mobilize immune cells (T-lymphocytes) to fight external damage (antigen), enter the epidermis from the bone marrow. The cells of the surface layer of the skin are actively involved in the reactions of humoral immunity, contributing to the production of antibodies. All these mechanisms lead to strong cutaneous immunity.

The skin is one of the immune organs along with the lymph nodes, bone marrow and thymus gland.

Secretory

The skin glands secrete 20 grams of sebum per day. It provides elasticity to the epidermis and, together with sweat, creates a protective environment on the surface layer of the skin.

Most of the sebaceous glands are on the skin of the face, scalp, between the shoulder blades, in the center of the chest, and also in the perineum. It is these parts that most often suffer from acne and.

So, human skin is an amazing organ that shelters and protects it from an aggressive external environment. Taking care of your skin will help not only to prolong its beauty, but also to preserve the health of the whole organism.

Leather is the shell of the body. Surprisingly resilient and durable, it protects us from germs and external influences, helps maintain a constant body temperature, flushes out some of the body's waste through the pores, and renews itself regularly. In addition, the skin contains receptors that send signals to the spinal cord, ensuring its tactile function. So we can distinguish between cold and hot, smooth and rough.

What is leather made of?

The skin is the largest organ of our body, it covers an area of at least 2 square meters. m!

In the skin, two main layers are distinguished - the epidermis and the dermis (the skin itself), as well as a thinner layer - the hypodermis or subcutaneous tissue. Epidermis: The outer layer of the skin that contains melanocytes - cells that produce melanin that act when we sunbathe. This layer also contains the stratum corneum keratin, a protein also present in hair, nails and body hairs. When exposed to sunlight, vitamin D is produced in the epidermis, which retains calcium in the bones. The epidermis is regularly renewed: dead cells on the surface of the skin are replaced with new ones. Dermis: A thick inner layer provides firmness and firmness to the skin. The dermis is riddled with blood vessels, sebaceous glands that secrete a fatty substance - sebum, sweat glands that are responsible for perspiration, sensitive receptors that respond to touch or pressure, and nerve endings that send information about the outside temperature to the brain. Hypodermis: A thin layer of fat, located under the dermis, acts as an insulating material. With age, the skin becomes wrinkled due to the gradual wear and tear of the dermis.

Three layers are distinguished in the skin: epidermis, dermis (skin itself) and hypodermis (subcutaneous tissue)
1. The surface of the skin is covered with hairs
2. The outer layer of the skin is called the epidermis.
3. The inner layer of the skin is called the dermis
4. Under the layer of the dermis is the hypodermis

What is leather for?

It is a natural barrier that protects against aggressive external environment and microbes. The skin also helps to regulate the internal body temperature: if we are hot, we sweat, thus refreshing the body. If we are cold, we shiver or become covered with "goose bumps" - this helps the body to keep warm.

Leather in all colors

Melanin is responsible for skin color. But the amount of this pigment is different for everyone. If there is a lot of melanin in all layers of the skin, then the skin is black. If melanin is present only in the deep layers of the epidermis, the skin is light. If melanin is combined with another substance, carotene, the skin has a yellow honeydew. Fair-haired people, whose skin produces little melanin, usually sunburn if they do not protect their skin with special means. But the skin of a dark-haired person can also "burn" if he is under the sun without protection.

Skin weight ranges from 3 to 5 kg in different people.