Types of acne

Read also

Retinoids

Types of retinoids

Read also

Eyelash care

Eyelash growth products

Prostaglandins for the growth of long eyelashes

List of prostaglandins

We analyze eyelash growth products by ingredients

Read also

Fight against aging (anti-aging)

The structure and main functions of human skin

Human skin renewal period

Skin is a tissue: elastic, porous, durable, waterproof, antibacterial, sensitive, which can maintain heat balance, protect against the harmful effects of the external environment, secrete fat, preserve the skin, produce odorous substances and recover (regenerate), as well as absorb some necessary chemical elements and reject others, protect our body from the adverse effects of sunlight.

The pH of human skin is 3.8-5.6.

There are approximately 5 million hairs on the surface of human skin. For every square centimeter of human skin, there are an average of 100 pores and 200 receptors.

Which layers of the skin can be affected by cosmetics?

Since cosmetic (cosmeceutical products) can penetrate deeply, can cosmetics reach the dermis?

According to the laws of most countries, a cosmetic product can only have an external effect. This means that no cosmetic additives should reach the living layers of the skin and act on them. Cosmetic preparations can and must interact only with the dead substances of the skin and under no circumstances should reach its living layers and, moreover, affect them. That is the purpose of cosmetics.

However, in the lower part of the epidermis there is no "shutter" that prevents the penetration of substances into the depths of the dermis (into the blood and lymphatic vessels). The presence of an effective exchange between the epidermis and dermis is confirmed by experimental data. Substances that have overcome the transepidermal barrier, with a certain degree of probability, enter the bloodstream and, in accordance with this, are able to affect all tissues of the body.

What substances are able to penetrate deep into the skin, overcome the transepidermal barrier and enter the dermis?

Proven to penetrate deep into the skin: nicatin, caffeine, nitroglycerin, essential oils(they are enhancers, they are found in the bloodstream), vitamin E lingers at the junction of the epidermis and dermis, hyaluronic acid reaches the dermis 30 minutes after application, and then enters the bloodstream (source: Journal of Investigative Dermatology). Scientists from the University of Rochester (University of Rochester Medical Center) came to the conclusion that the nanoparticles that are part of sunscreens penetrate deep into the skin. Liposomes are nanoparticles that easily penetrate into the deeper layers of the skin and deliver the necessary nutrients there.

Structure of the Skin

The secret of the amazing multifunctionality of the skin lies in its structure. The skin is made up of 3 important layers:

• 1. The outer layer is the epidermis,
• 2. The inner layer is the dermis,
• 3. Subcutaneous base - hypodermis.

Each layer performs a specific function.

In different parts of the body, the thickness and color of the skin, the number of sweat, sebaceous glands, hair follicles and nerves are not the same.

It is believed that the skin is only a few millimeters thick, but if the skin constantly needs protection, then it becomes thicker, this is a defense mechanism that everyone has. Therefore, in some places the skin is thicker, in others thinner. The soles and palms have a denser epidermis and a layer of keratin.

As for hairiness, for example, there are many hair follicles on the top of the head, but none on the soles. The tips of the fingers and toes contain many nerves and are extremely sensitive to touch.

The structure and properties of human skin: Epidermis

The epidermis is the upper stratum corneum of the skin, which is formed by stratified epithelium. In the deep layers of the epidermis, the cells are alive, there they divide and gradually move to the outer surface of the skin. At the same time, the skin cells themselves die and turn into horny scales, which are peeled off and removed from its surface.

The epidermis is practically impermeable to water and solutions based on it. Fat-soluble substances penetrate the epidermis better due to the fact that cell membranes contain a large amount of fats and these substances seem to “dissolve” in cell membranes.

There are no blood vessels in the epidermis, its nutrition occurs due to the diffusion of tissue fluid from the underlying layer of the dermis. The intercellular fluid is a mixture of lymph and blood plasma flowing from the terminal loops of the capillaries and returning to the lymphatic and circulatory systems under the influence of heart contractions.

What cells make up the epidermis?

Most epidermal cells produce keratin. These cells are called keratinocytes (spiky, basal, and granular). Keratinocytes are in constant motion. Young keratinocytes are born during the division of the germ cells of the basement membrane, located at the border of the epidermis and dermis. As they grow older, the keratinocyte moves to the upper layers, first to the spiny layer, then to the granular one. At the same time, keratin, a particularly strong protein, is synthesized and accumulated in the cell.

Eventually, the keratinocyte loses its nucleus and major organelles and turns into a flat "pouch" stuffed with keratin. From that moment on, it receives a new name - "corneocyte". Corneocytes are flat scales that form the stratum corneum (obsolete cells of the epidermis) responsible for the barrier function of the epidermis.

The corneocyte continues to move up and, having reached the surface of the skin, exfoliates. A new one takes its place. Typically, the life span of a keratinocyte lasts 2-4 weeks. In childhood, the process of renewal of epidermal cells is more active, and slows down with age.

Corneocytes are held together by a plastic "cement" consisting of a double layer of special lipids - ceramides (ceramides). molecules ceramides (ceramides) and phospholipids have hydrophilic "heads" (fragments that love water) and lipophilic "tails" (fragments that prefer fats).

Melanocytes are found in the basal layer of the skin (basement membrane) and produce melanin. These are the cells that produce the pigment melanin, which gives skin its color. Thanks to melanin, the skin protects a person to a large extent from radiation: infrared rays are completely blocked by the skin, ultraviolet rays are only partially. In some cases, the formation of age spots depends on the state of the basement membrane.

There are in the epidermis and special Langerhans cells, which perform the function of protection against foreign bodies and microbes.

What is the thickness of the epidermis?

The thickness of the epidermis is approximately equal to 0.07 - 0.12 millimeters (this is the thickness of a plastic film or paper sheet), the especially rough skin of our body can reach a thickness of 2 mm.

The thickness of the epidermis is heterogeneous: in different places of the skin it is different. The thickest epidermis, with a pronounced keratinized layer, is located on the soles, a little thinner on the palms, and even thinner on the genitals and skin of the eyelids.

How many days does the complete renewal of the epidermis take?

Depends on the state of the epidermis appearance skin, its freshness and color. The epidermis consists of dead cells, which are replaced by new ones. Due to the constant renewal of cells, we lose about 10 billion cells a day, this is a continuous process. During a lifetime, we shed about 18 kilograms of skin with keratinized cells.

When the skin is exfoliated, it is cleansed - this is a necessary process of skin renewal, in which, together with dead cells, all substances harmful to the skin are removed: the cells carry away dust, microbes, substances secreted by the sweat glands (urea, acetone, bile acids come to the surface along with sweat). pigments, salts, toxic substances, ammonia, etc.). and much more. The skin does not allow the army of microbes to reach us: during the day, our skin is attacked by 1 cm from 100,000 to several million of all kinds of microbes. However, if the skin is healthy, it becomes impervious to them.

The younger and healthier the skin, the more intense the process of its renewal. New cells push out old ones, old ones are washed away after we take a shower, wash, sleep, put on clothes. With age, cell renewal occurs less and less, the skin begins to age, wrinkles appear.

The epidermis is separated from the dermis by a basement membrane (it consists of elastin and collagen fibers) with a germ layer of continuously dividing cells, which gradually move from the basement membrane to the surface of the skin, where they then peel and fall off. The epidermis is completely renewed, exactly replaced by a completely new layer: a mole remains a mole, dimples remain dimples, freckles freckles, cells accurately reproduce at the genetic level how the skin should look in accordance with the individual characteristics of each individual person.

The process of cell movement from the basement membrane to desquamation and shedding from the surface of the skin into young age equals 21-28 days, and then happens less and less. Starting at about 25 years of age, the process of skin renewal becomes slower and increases to 35-45 days by the age of 40 and 56-72 days after the age of 50. This is the reason for the use of anti-aging and regenerating drugs for a period of at least a month, and for a more mature age - at least 2-3 months.

The process of cell division and promotion mature skin not only slowed down, but also heterogeneous in different areas, which also affects the aesthetic appearance of the skin. If dead skin cells build up, the process of cell division occurs more slowly, which leads to faster aging of the skin. In addition, the layering of dead cells complicates the penetration of oxygen and nutrients into the skin.

How many layers does the epidermis contain?

The epidermis consists of 12-15 layers of the stratum corneum. However, depending on the structure, the epidermis can be divided into five main zones (layers): basal, prickly, granular, shiny and horny. Upper (outer) epidermis layer and consists of already dead cells without nuclei, the inner one consists of living cells that are still capable of dividing.

Fragments of the stratum corneum, lustrous, and granular layers that do not have the ability to divide can be attributed to dead skin structures, and, accordingly, the boundary between "living and dead" substances should be located somewhere in the spinous layer.

1. Basal layer of the epidermis (growth)

The basal layer is the innermost layer of the epidermis closest to the dermis. It consists of a prismatic single-row epithelium and a large number of slit-like spaces.

The bulk of the cells here are keratinocytes containing chromatin and melanin.

Between the basal keratinocytes are melanocytes containing great amount melanin. Melanin is formed in these cells from tyrosine in the presence of copper ions. This process is regulated by melanocyte-stimulating pituitary hormone, as well as catecholamines: adrenaline and norepinephrine; thyroxine, triiodothyronine and androgens. The synthesis of melatonin increases when the skin is exposed to ultraviolet radiation. Vitamin C plays a significant role in the synthesis of melanin.

Among the cells of the basal epithelium there are few specific tactile (Merkel) cells. They are larger than keratinocytes in size, contain osmiophilic granules.

The basal layer provides attachment of the epidermis to the underlying skin and contains cambial epithelial elements.

2. Spiny layer of the epidermis (stratum spinosum)

Above the basal layer is prickly (stratum spinosum). In this layer, keratinocytes are located in several layers.

The cells of the spinous layer are large, their shape is irregular, gradually becoming flattened when approaching the granular layer. The cells of the spiny layer contain spines at the sites of intercellular contacts.

In the cytoplasm of spiny cells there are keratinosomes - granules containing lipids - ceramides. The cells of the spinous layer secrete ceramides outward, which, in turn, fill the space between the cells in the layers above. Thus, the keratinized stratified squamous epithelium becomes impermeable to various substances.

In addition, there are also desmosomes - specialized cell structures.

Keratinocytes in the stratum spinosum contain very little chromatin, so they are paler. They have one feature: in their cytoplasm there are many special thin tonofibrils.

3. Granular layer of the epidermis (stratum granulosum)

The granular (keratohyalin) layer (stratum granulosum) consists of spiny keratinocytes and process epidermocytes. It is assumed that these cells are "wandering" epidermal macrophages that perform a protective function.

In the granular layer, there are from 1-3 on the palms and 5-7 on the soles of layers of flat cells, closely adjacent to each other. Their oval nuclei are poor in chromatin. A feature of the cells of the granular layer is the peculiar grains in their cytoplasm, consisting of a substance similar in structure to DNA.

There are two main types of granules located in the cytoplasm of cells of the granular layer: keratoglanic and lamellar. The former are necessary for the formation of keratin, while the latter provide moisture impermeability of the skin by releasing special lipid molecules on its surface.

4. Shiny (eleidine, transparent) layer of the epidermis (stratum lucidum)

The shiny layer (stratum lucidum) is above the granular layer. This layer is quite thin, and is clearly visible only in those areas where the epidermis is most pronounced - on the skin of the palms and soles.

It is not located on all areas of the skin, but only where the thickness of the epidermis is significant (palms and soles), and is completely absent on the face. Consists of 1-3 rows of flat cells, most of which do not contain nuclei.

Flat, homogeneous keratinocytes are the main cellular elements of this layer. The shiny layer is inherently transitional from living epithelial cells to keratinized scales located on the very surface of human skin.

5. The stratum corneum of the epidermis (stratum corneum)

The stratum corneum (stratum corneum) is the layer of the epidermis that is in direct contact with the external environment.

Its thickness varies in different parts of the skin, and very significantly. The most developed stratum corneum is on the palms and soles, much thinner on the abdomen, flexion surfaces of the arms and legs, sides, skin of the eyelids and genitals.

The stratum corneum has in its composition only thin non-nuclear cells that are tightly adjacent to each other. Horny scales consist of keratin - a substance of an albuminoid nature, containing sulfur in excess, but little water. The scales of the stratum corneum are tightly connected to each other and provide a mechanical barrier to microorganisms.

The structure and properties of human skin: Dermis

The dermis is the inner layer of the skin, the thickness of which is from 0.5 to 5 mm, the largest on the back, shoulders, and hips.

In the dermis there are hair follicles (from which hair grows), as well as a huge number of the thinnest blood and lymphatic vessels that provide nutrition to the skin, contraction and relaxation of blood vessels allows the skin to retain heat (thermoregulatory function). The dermis contains pain and sensory receptors and nerves (which branch into all layers of the skin and are responsible for its sensitivity).

In the dermis there are also functional glands of the skin, through which excess water and salts are removed (excretory function): sweat glands (produce sweat) and sebaceous glands (produce sebum). The sebaceous glands produce the necessary amount of sebum, which protects the skin from aggressive external influences: it makes the skin waterproof, bactericidal (sebum, together with sweat, creates an acidic environment on the skin surface, which adversely affects microorganisms). Sweat glands help maintain a constant body temperature, preventing overheating by cooling the skin through sweat.

How many layers does the dermis contain?

The dermis includes two layers: the reticular and papillary layers.

The reticular layer consists of loose connective tissue. This tissue includes an extracellular matrix (we will talk about it in more detail below) and cellular elements.

The papillary layer protrudes into the epidermis and forms the skin papillae. These papillae create a special unique "pattern" of our skin and are especially visible on the balls of our fingers and the soles of our feet. It is the papillary layer that is responsible for "fingerprints"!

The basis of the cells in the dermis is fibroblast, which synthesizes extracellular matrix, including collagen, hyaluronic acid and elastin.

What is the extracellular matrix and what does it consist of?

The composition of the extracellular matrix includes two main components: the fibrillar part and the matrix.

fibrillar part- these are collagen, elastin, and reticulin fibers that create the skin frame. Collagen fibers are intertwined with each other, thus creating an elastic network. This network is located almost on the surface of the skin under the epidermis and makes up the skeleton, which gives the skin strength and elasticity.

In the face area, collagen fibers create a special dense network. The collagen fibers in it are so strictly stacked and ordered that they form lines of the least stretch. They are known as the Langer lines. They are known to cosmetologists and masseurs: they massage the face along the Langer lines and apply any cosmetics. This is done in order not to load the skin, not to stretch it, thus provoking the formation of wrinkles.

In youth, the framework of collagen fibers is strong and able to ensure the mobility and flexibility of the skin, maintaining its elasticity and shape. Unfortunately, our female age is short ...

I really liked the comparison of the skin with the Soviet bed, which is based on a metal mesh. The iron springs of the new bed quickly return to their original position, but from the load, the frame springs begin to sag and soon our bed loses its shape. Our skin also works - young springs (collagen fibers) keep their shape perfectly, but with age they sag and become flabby. Whatever great mattress we put on the surface, it will not solve our problem.

Matrix (matrix or amorphous component) its structure resembles a gel and consists of polysaccharides. The more famous polysaccharides are chitosan, seaweed polysaccharides, hyaluronic acid.

It is the components of the extracellular matrix, both amorphous and fibrillar, that create the skin from the inside. By themselves, saccharides do not form fibers, but they fill all the gaps between connecting cells and fibers. It is through them that the interstitial transport of all substances occurs.

As a result, it is the state of the dermis (water content in the polysaccharide gel, the integrity of collagen fibers, etc.) that determines the state of the epidermis and the healthy appearance of the skin.

The structure and properties of human skin: Hypodermis (subcutaneous fatty tissue)

The hypodermis is the subcutaneous base (fat layer), protects our body from excess heat and cold (allows us to retain heat inside us), acting as a thermal insulator, softens the fall from shock.

Subcutaneous adipose tissue - a storehouse of vitamins

Fat cells also represent a depot in which fat-soluble vitamins (A, E, F, K) can be stored.

Less fat - more wrinkles

Subcutaneous adipose tissue is very important as a mechanical support for the outer layers of the skin. The skin, in which this layer is weakly expressed, usually has more wrinkles and folds, and "ages" faster.

The more fat, the more estrogen

An important function of adipose tissue is hormone-producing. Adipose tissue is able to accumulate estrogens in itself and can even stimulate their synthesis (production). Thus, you can get into a vicious circle: the more subcutaneous fat we have, the more estrogen is produced. This is especially dangerous for men, since estrogenic hormones suppress their production of androgens, which can lead to the development of hypogonadism. This leads to a deterioration in the work of the gonads and leads to a decrease in the production of male sex hormones.

It is very important for us to know that adipose tissue cells contain a special enzyme - aromatase. It is with its help that the process of estrogen synthesis by adipose tissue is carried out. Guess where is the most active aromatase? That's right, in fatty tissue on the hips and buttocks!

What is responsible for our appetite and satiety?

Our adipose tissue contains another very interesting substance - leptin. Leptin is a unique hormone that is responsible for the feeling of satiety. Leptin allows our body to regulate appetite and through it the amount of fat in the subcutaneous tissue.

Article navigation

Leather- this is one of the human organs that perform a protective role and a number of biological functions. The entire human body is covered with skin, and depending on height and weight, its area is from 1.5 to 2 m 2, and its weight is from 4 to 6% of the human mass (excluding hypodermis).

The article discusses the structure of human skin, its structure and functions of each layer, how skin cells are formed and renewed and how they die.

Skin functions

The main purpose of the skin It is, of course, protection against external influences. environment. But our skin is multifunctional and complex and takes part in a number of biological processes in the body.

The main functions of the skin:

• mechanical protection- skin prevents soft tissues from mechanical impact, radiation, microbes and bacteria, ingress of foreign bodies into tissues.
• UV protection- under the influence of solar treatment, melanin is formed in the skin as a protective reaction to external adverse (with prolonged exposure to the sun) effects. Melanin causes temporary coloration of the skin in more dark color. A temporary increase in the amount of melanin in the skin increases its ability to retain ultraviolet (delays more than 90% of radiation) and helps neutralize free radicals formed in the skin when exposed to the sun (acts as an antioxidant).

• thermoregulation- participates in the process of maintaining a constant temperature of the whole organism, due to the work of the sweat glands and the thermal insulating properties of the layer hypodermis consisting mainly of adipose tissue.
• tactile sensations- due to nerve endings and various receptors close to the skin surface, a person feels the influence of the external environment in the form of tactile sensations (touch), and also perceives temperature changes.
• maintaining water balance- through the skin, the body, if necessary, can excrete up to 3 liters of fluid per day through the sweat glands.
• metabolic processes- through the skin, the body partially removes by-products of its vital activity (urea, acetone, bile pigments, salts, toxic substances, ammonia, etc.). Also, the body is able to absorb some biological elements from the environment (trace elements, vitamins, etc.), including oxygen (2% of the total gas exchange of the body).
• vitamin synthesisD- under the influence of ultraviolet radiation (sun), vitamin D is synthesized in the inner layers of the skin, which is subsequently absorbed by the body for its needs.

Skin structure

The skin is made up of three main layers:

• epidermis(epidermis)
• dermis(corium)
• hypodermis(subcutis) or subcutaneous adipose tissue

In turn, each layer of the skin consists of its own individual structures and cells. Consider the structure of each layer in more detail.

Epidermis

Epidermis- this is the top layer of the skin, formed mainly on the basis of keratin protein and consisting of five layers:

• horny- the uppermost layer, consists of several layers of keratinized epithelial cells, called corneocytes (horny plates), which contain insoluble protein keratin
• brilliant- consists of 3-4 rows of cells, elongated in shape, with an irregular contour geometric shape containing eleidine, from which keratin
• grainy- consists of 2-3 rows of cells of a cylindrical or cubic shape, and closer to the surface of the skin - diamond-shaped
• prickly- consists of 3-6 rows spiny keratinocytes, polygonal shape
• basal- the lowest layer of the epidermis, consists of 1 row of cells called basal keratinocytes and having a cylindrical shape.

The epidermis does not contain blood vessels, so the intake nutrients from the inner layers of the skin to the epidermis going on at the expense diffusion(penetration of one substance into another) tissue(intercellular) liquids from the dermis into the layers of the epidermis.

interstitial fluid It is a mixture of lymph and blood plasma. It fills the space between cells. Tissue fluid enters the intercellular space from the terminal loops of blood capillaries. There is a constant exchange of substances between the tissue fluid and the circulatory system. Blood delivers nutrients to the intercellular space and removes waste products of cells through the lymphatic system.

The thickness of the epidermis is approximately equal to 0.07 - 0.12 mm, which is equal to the thickness of a simple paper sheet.

In some parts of the body, the thickness of the epidermis is slightly thicker and can be up to 2 mm. The most developed stratum corneum is on the palms and soles, much thinner on the abdomen, flexion surfaces of the arms and legs, sides, skin of the eyelids and genitals.

Skin acidity pH is 3.8-5.6.

How does human skin cells grow?

In the basal layer of the epidermis cell division occurs, their growth and subsequent movement to the outer stratum corneum. As the cell matures and approaches the stratum corneum, keratin protein accumulates in it. Cells lose their nucleus and major organelles, turning into a "pouch" filled with keratin. As a result, the cells die, and form the uppermost layer of the skin from keratinized scales. These scales are shed over time from the surface of the skin and replaced by new cells.

The whole process from the origin of the cell to its exfoliation from the surface of the skin takes an average of 2-4 weeks.

Skin permeability

The scales that make up the uppermost layer of the epidermis are called - corneocytes. The scales of the stratum corneum (corneocytes) are interconnected by lipids consisting of ceramides and phospholipids. Due to the lipid layer, the stratum corneum is practically impermeable to aqueous solutions, but solutions based on fat-soluble substances are able to penetrate through it.

Color of the skin

Cells within the basal layer melanocytes, which highlight melanin- a substance that determines the color of the skin. Melanin is formed from tyrosine in the presence of copper ions and vitamin C under the control of hormones secreted by the pituitary gland. The more melanin contained in one cell, the darker the color of human skin. The higher the melanin content in the cell, the better the skin protects against ultraviolet radiation.

With intense exposure to the skin of ultraviolet radiation, the production of melanin sharply increases in the skin, which provides the skin with a tan.

The effect of cosmetics on the skin

All cosmetics and procedures, designed for skin care, affect mainly only the top layer of the skin - epidermis.

Dermis

Dermis- this is the inner layer of the skin, from 0.5 to 5 mm thick, depending on the part of the body. The dermis is made up of living cells., supplied with blood and lymphatic vessels, contains hair follicles, sweat glands, various receptors and nerve endings. The basis of the cells in the dermis is fibroplast, which synthesizes the extracellular matrix, including collagen, hyaluronic acid and elastin.

The dermis is made up of two layers:

• reticulate(pars reticularis) - extends from the base of the papillary layer to the subcutaneous fatty tissue. Its structure is formed mainly from bundles of thick collagen fibers located parallel to the surface of the skin. The mesh layer contains lymphatic and blood vessels, hair follicles, nerve endings, glands, elastic, collagen and other fibers. This layer provides the skin with firmness and elasticity.
• papillary (pars papillaris), consisting of an amorphous structureless substance and thin connective tissue (collagen, elastic and reticular) fibers that form papillae that lie between the epithelial ridges of spiny cells.

Hypodermis (subcutaneous adipose tissue)

Hypodermis- This is a layer consisting mainly of adipose tissue, which acts as a heat insulator, protecting the body from temperature changes.

The hypodermis accumulates nutrients necessary for skin cells, including fat-soluble vitamins (A, E, F, K).

The thickness of the hypodermis varies from 2 mm (on the skull) to 10 cm or more (on the buttocks).

With inflammatory processes in the hypodermis that occur during certain diseases, cellulite occurs.

Video: Skin structure

• The area of ​​​​the entire skin of an adult is 1.5 - 2 m 2
• One square centimeter of skin contains:

• over 6 million cells
• up to 250 glands, of which 200 sweat and 50 sebaceous
• 500 different receptors
• 2 meters of blood capillaries
• up to 20 hair follicles

• With an active load or high external temperature, the skin can release more than 3 liters of sweat per day through the sweat glands.
• Due to the constant renewal of cells, we lose about 10 billion cells a day, this is a continuous process. Over the course of a lifetime, we shed about 18 kilograms of skin with keratinized cells.

Skin cells and their function

The skin is made up of a large number various cells. To understand the processes occurring in the skin, it is good to have a general idea of ​​the cells themselves. Consider what the various structures are responsible for (organelles) in a cage:

• cell nucleus- contains hereditary information in the form of DNA molecules. In the nucleus, replication occurs - doubling (multiplication) of DNA molecules and the synthesis of RNA molecules on a DNA molecule.
• kernel shell- provides exchange of substances between the cytoplasm and the nucleus of the cell
• cell nucleolus- it synthesizes ribosomal RNA and ribosomes

• cytoplasm- a semi-liquid substance that fills the interior of the cell. Cellular metabolism takes place in the cytoplasm
• ribosomes- necessary for the synthesis of proteins from amino acids according to a given matrix based on genetic information embedded in RNA (ribonucleic acid)
• vesicle- small formations (containers) inside the cell in which nutrients are stored or transported
• apparatus (complex) Golgi is a complex structure that is involved in the synthesis, modification, accumulation, sorting of various substances inside the cell. It also performs the functions of transporting substances synthesized in the cell through the cell membrane, beyond its limits.
• mitochondrion- the energy station of the cell, in which the oxidation of organic compounds occurs and the release of energy during their decay. generates electrical energy in the human body. An important component of the cell, the change in activity of which over time leads to aging of the body.
• lysosomes- necessary for the digestion of nutrients inside the cell
• interstitial fluid fills the space between cells and contains nutrients

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

The structure of the outer cover of the body

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

Having figured out what the epidermis is, finding out where it is located, many begin to be interested in its structure. It consists of cells of various shapes and structures. They reflect certain phases of their lives. The thickness of the epidermis, depending on its location, can be from 0.07 mm to 1.4 mm. The thickest layer is on the soles of the feet, palms. And the most (its upper layer) is in the pubic region, on the forearms, and the abdomen.

The structure of the upper keratinized cover

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

• basal (embryonic);
• spiny;
• grainy;
• brilliant;
• horny.

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

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

stratum corneum

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

Due to this, these keratinized components of the layer can protect the underlying tissues from mechanical damage, temperature fluctuations, drying and penetration of bacteria. Horny scales are divided into two types. They may have loose or dense filling of keratin fibrils. On the surface are the second of them. And the first are located closer to the granular layer. In their structure, you can find the remnants of the cell organelles that were previously in them. These scales are often referred to as T-cells.

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

glitter layer

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

Granular layer

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

Spiny cells

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

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

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

Basal cells

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

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

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

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

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

STRUCTURE OF THE SKIN

Epidermis- the surface layer of the skin, consisting of various layers of epithelial cells, in contact with the external environment. Its thickness in various parts of the body ranges from 0.05 to 0.5 mm. The epidermis is an epithelial tissue consisting of closely spaced cells that do not contain any intercellular elements. The cells of the epidermis are arranged in such a way that they make up four or five layers, depending on the area of ​​​​the skin.

Dermis- the middle layer of the skin, consisting of cells and threads of the connective tissue, where all the glands and receptors are located, which ensure the implementation of the basic and sensory functions of the skin.

Hypodermis- the deepest layer of the skin, different in depth on different parts of the body and mainly consisting of adipose tissue, which forms the basis of the body's energy reserve and is a thermal insulator.

The dermis, located under the epidermis, is separated from it by a thick basement membrane with numerous folds: they look like conical elevations towards the epidermis; the papillae of the dermis are located on the elevations of the epidermis, the projections of which, being the interpapillary ridges, go into the dermis. This increases the surface area between the two layers - this is very important, since the nutrition of the cells of the epidermis depends on blood vessels that reach only the dermis.

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

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

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

Skin: what is it

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

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

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

What are the functions of the skin

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

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

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

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

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

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

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

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

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

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

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

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

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

What is leather made of?

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

Epidermis

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

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

Structure

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

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

5 epidermal layers

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

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

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

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

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

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

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

Types of epidermal cells

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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