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 one source, but are located at different levels depending on the degree of maturation. The epidermis is the first universal barrier faced by any environmental factor potentially dangerous to the body.
Layered 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. Also in the dermis are hair. Moreover, their "ancestor", like nails, is the epidermis. What it is? This is the stratum corneum, located directly above the dermis and plays a protective role not only in relation to it, but also the whole organism. A little deeper than the dermis is the less important layer of the skin - fiber, where fat accumulates in adipocytes.
The layered structure of the epidermis
The deepest layer is the basal, which is entirely represented by cells capable of division. Due to them, the damaged cells are restored and the lost horny scales are replenished. In the thickness of the basal layer are single melanocytes that accumulate a black pigment substance (melanin), which is necessary for ultraviolet skin protection.
A prickly layer is located above the basal and is built in the form of 3-8 rows of living cells, already incapable of division. They are linked to each other through cytoplasmic outgrowths to give the skin mechanical strength. In areas of the skin subjected to frequent external influences, the number of layers of prickly 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 corns.
Immediately above the prickly layer is a 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 oriented parallel to the skin surface.
Shiny is a layer of cells that are 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 effects.
Epidermal cell function
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, this is not all the roles that the epidermis plays. What is it and how is it explained?
- First, the surface layer distinguishes between the environment of the body and the outside world to protect the body and to prevent leakage of important substances and components.
- Secondly, the epidermis protects well from low-power ionizing corpuscular and wave radiation, with which the body daily encounters.
- Thirdly, the epidermis of the skin is a good chemical barrier preventing the ingress and absorption of hydrophilic substances. Moreover, lipophilic (fat soluble) are well absorbed by them.
- And the last on the list, but therefore 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 in this is played by the epidermis. What it is? This is a good mechanical barrier that simply does not allow a virus, bacteria, fungus or parasite to enter the body, causing inflammatory processes there.
Without melanocytes and keratinized cells, the functions of the epidermis would not have been realized. Epithelial cells play the role of a mechanical barrier, and melanocytes - the optical. 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 those conditions that are observed in the familiar world. After all, it was the development of the skin that allowed those organisms from which the person came to get out of the water and conquer the land.
The main features of the epidermis
All skin layers phylogenetically developed in order 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 secretion by sweat glands. There is no other physiological way to leak fluid from the body through the skin.
If we consider the epidermis from a cosmetic point of view, then the following facts are obvious. This layer of skin cannot have wrinkles and scars; it has no blood vessels. It feeds on the diffusion of substances from the vessels of the dermis of the skin. Therefore, its only cosmetic problems are the following: hyperkeratosis (thickened layers of the epidermis) and peeling of the skin. The fight against these phenomena, as well as with 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 it is and how these conditions appear, read below. The first category is diseases associated with increased reproduction of 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 epidermal diseases is tumor. From the epidermis, basal cell carcinoma and melanoma can develop. The latter originates from melanocytes.