Skin, according to many dermatologists, is the most complex human organ. The presence of many layers and various functions, an abundant network of blood vessels and entire groups of nerve receptors provide it with the main place in protecting a person from environmental factors. Moreover, the skin also plays a communicative role, having the ability to receive tactile information from the outside world. And although the epidermis as the top layer is important only as a mechanical barrier, its value is very high.
General characteristics of the epidermis
The layer of dividing, maturing, dying and already dead cells is the epidermis. What it is? This is a whole tissue that has several layers, the cells of which come from the same source, but are located at different levels depending on the degree of maturation. The epidermis is the first universal barrier that any environmental factor potentially dangerous to the body faces.
Layer structure: skin layers
The structure of the skin is layered - 3 layers that perform different functions. The most important of these is the dermal, which has blood vessels, receptors, and muscles. Hair is also located in the dermis. Moreover, their "ancestor", like nails, is the epidermis. What it is? This is the stratum corneum, located directly above the dermis and playing a protective role not only in relation to it, but to the whole organism. A little deeper than the dermis is a less important layer of the skin - fiber, where fat accumulates in adipocytes.
Layered structure of the epidermis
The deepest layer is the basal layer, which is entirely represented by cells capable of dividing. Due to them, damaged cells are restored and lost horny scales are replenished. In the thickness of the basal layer, there are single melanocytes that accumulate a black pigment substance (melanin), which is necessary for ultraviolet skin protection.
The spiny layer is located above the basal layer and is built in the form of 3-8 rows of living cells, already incapable of division. They are linked to each other by means of cytoplasmic outgrowths to give the skin mechanical strength. In areas of the skin exposed to frequent external influences, the number of layers of spiny cells increases to 8-10 pieces. In such places there are no sweat glands and hair: feet and palms. With frequent damage to other areas, the layers of the epidermis also thicken with the formation of calluses.
Immediately above the spiny layer is the granular layer, which is represented by half-dead epidermal cells. Their organelles lose their ability to generate energy, but accumulate a significant amount of tonofibrils. The granular layer consists of only 1-2 cell layers orientedparallel to the surface of the skin.
Brilliant is a layer of cells completely devoid of organelles. Their purpose is mechanical protection of the skin and gradual death, degradation to the stratum corneum. The latter is superficial. This is a collection of dead squamous cells, which are an excellent barrier to pathogenic attacks.
Functions of epidermal cells
The main function of the epidermis is the creation of mechanical, physical, biological and chemical barriers that delimit the internal environment of the body from potential and actually pathogenic factors. However, these are not all the roles played by the epidermis. What is it, and how is it explained?
- First, the surface layer separates the body environment from the outside world to protect the body and prevent leakage of important substances and components.
- Secondly, the epidermis protects well from low-power ionizing corpuscular and wave radiation that the body encounters daily.
- Thirdly, the epidermis of the skin is a good chemical barrier that prevents the ingress and absorption of hydrophilic substances. Moreover, lipophilic (fat-soluble) are well absorbed by them.
- And the last in the list, but no less important function is biological protection. There are very few bacteria and fungi that can infect humans through the skin. The main protective role is played by the epidermis. What it is? This is a good mechanical barrier that simply does not allow the virus to enter,bacteria, fungus or parasite inside the body, causing inflammation there.
Without melanocytes and keratinized cells, the functions of the epidermis would not be realized. Epithelial cells play the role of a mechanical barrier, and melanocytes - an optical one. This means that the epidermis protects against damage and evaporation of the liquid, and pigment cells - from ultraviolet radiation. All this allowed a person to adapt to the conditions that are observed in the familiar world. After all, it was the development of the skin that allowed those organisms from which man originated to emerge from the water and conquer the land.
Main features of the epidermis
All layers of the skin evolved phylogenetically to provide certain functions. The epidermis is designed to protect the dermis from mechanical, physical and chemical influences. It is needed to limit the loss of fluid, which can only evaporate from its surface after being secreted by the sweat glands. There is no other physiological way for fluid to leak from the body through the skin.
If we consider the epidermis from a cosmetic point of view, the following facts are obvious. This layer of skin cannot have wrinkles and scars, and there are no blood vessels in it. It is nourished by the diffusion of substances from the vessels of the dermis of the skin. Therefore, his only cosmetic problems are the following: hyperkeratosis (thickened layers of the epidermis) and flaking of the skin. The fight against these phenomena, as well as against psoriasis, requires treatment and the use of cosmetics.
Pathologies of the epidermis and melanocytes
There are several categories of diseases that the epidermis can suffer from. What is it and how these states manifest themselves, read below. The first category is diseases associated with increased reproduction of the epidermal cells of the basal layer. The disease is called psoriasis. There is also a congenital condition - ichthyosis, in which the baby is already born with hyperkeratosis and is not viable. The second group of diseases of the epidermis is tumor. Basalioma and melanoma can develop from the epidermis. The latter originates from melanocytes.
