Remember Luc Besson's wonderful film "The Fifth Element"? At the beginning of the film, scientists from a futuristic laboratory were recreating a human body from preserved cells. After the restoration of bone tissue and muscles, the scientist says:
The last stage. Irradiation of cells with ultraviolet light stimulates the protective reaction of the body, that is, the skin builds up.
Despite the fact that the film belongs to the category of science fiction, the scientist did not lie, and the scriptwriters paid special attention to this important process. So what functions does the skin perform and what is its value for the human body? Let's find out.
Skin is the result of evolution
So, the structure and functions of the skin, and in general its presence is the result of millions of years of evolution. With the development of new species and populations, the covers changed, improved and adapted to new habitat conditions and environmental factors. According to the theory of evolution, the process of formation of the skin that we have today took place as follows:
- only invertebrates lived in the seas and oceans: sponges and jellyfish with a single-layer shell (cover);
- the first marine vertebrates that evolved from sponges and jellyfish acquired a two-layer shell and were able to produce protective mucus;
- first landed vertebrates gain another layer of skin that produces keratin proteins;
- Keratin proteins were transformed into an insulating layer, which appeared as skin.
Vertebrates living on land were exposed to ultraviolet rays (the sun), which played an important role in the evolutionary processes of the appearance of the skin. This is what the movie reference led to.
Building
The skin, like any other organ, is very complex: scientific articles have been written on this topic for several dozen pages. Therefore, let's try to figure it out without the subtleties of scientific topics, in simple and understandable words for everyone.
Skin consists of three layers: epidermis (upper), dermis (middle) and hypodermis (lower).
The hypodermis is a fatty layer, or, roughly speaking, fat. This is where all the bars and waffles we ate late at night are stored. The thickness of the hypodermis varies in the range (depending on the part of the body) 0.2-6 cm, obesity increases these figures by 2-3 times. The hypodermis does a lot of good deeds in the body, and its absence can lead to irreversible consequences, which is especially fraught for women. The main functions of adipose tissue are the regulation of the level of sex hormones and the protection of internal organs from bruises.
Derma - this is what we mean by the skin itself. By the way, the dermis takes most of the nutrient medium and the necessary moisture from fatty tissue andblood, which means that in the pursuit of youth, first of all, you should eat right, and not buy an expensive cream. The dermis is made up of collagen, elastin and proteoglycan. The first gives the skin elasticity, the second - elasticity, the third retains water.
And finally, the top layer - the epidermis, represented by just a few layers of cells. The main task of the epidermis is protection from pathogenic microorganisms. Between the epidermis and the dermis there is a basement membrane, which regulates the exchange processes between the layers and is an additional protective barrier.
Epidermal Appendages
The top layer of the skin (epidermis) is supplemented with appendages:
- Sweat glands apparently produce sweat. Mainly located in the axillary and groin areas, as well as on the face, palms, feet.
- The sebaceous glands gave a person such a nuisance as acne. But sebum is produced for a reason: it softens the skin and serves as a fatty lubricant for the hair. For this reason, the sebaceous glands are located next to the hair follicles.
- Hair is on the entire surface of the skin, except for the palms, feet, eyelids, lips and especially sensitive areas of the genitals. Hair on the head protects us from sunstroke or, conversely, from frostbite. But vellus hair is a vestige and does not play a significant role for a modern person.
- Nails are horny tissue protected by cuticles from infections. The main function of nails is to protect the nerve endings located in the terminal phalanges of the fingers.
The ability of the epidermis to regenerate
The skin is regenerated (renewed) around the clock. This is possible thanks to keratinocytes - cells, 80% consisting of collagen. Keratinocytes originate in the depths of the epidermis and within 2-4 weeks reach the upper layer of keratinized cells, and then die off. This process is necessary not only for constant renewal, but also to maintain the optimal thickness of the epidermis due to its protective function.
Skin regeneration is of two types:
- physiological - the natural process of renewal of epidermal cells;
- reparative - the process of healing as a result of mechanical damage.
Slow down regeneration processes
With every year of life, the process of renewal of epidermal cells slows down, which inevitably leads to the first signs of aging - wrinkles. It is generally accepted that the main cause of skin aging is its insufficient blood supply, resulting in nutrient deficiency and slowing down metabolic processes in cells. By the age of 25, the body begins to redirect the flow of fresh blood to the internal organs, which is why over the next 15-25 years the intensity of skin saturation with nutrients slowly but surely declines. If in a twenty-year-old person the epidermis is renewed in 14-28 days, then in a forty-year-old - in two months.
Functions of human skin
Imagine a man without skin. What is the risk and what could be the consequences? Immediately comes to mindpathogenic influence of the environment. And this is absolutely true! First of all, human skin performs the function of protection, that is, it provides a kind of barrier from pathogenic bacteria and adverse environmental factors. It also protects internal organs from blows and bruises, which is ensured by the softness and mobility of fatty tissue.
Additional skin features:
- cleansing - removes harmful metabolic products from the body through sweating;
- thermoregulatory - maintains the required temperature of the body by regulating the intensity of sweating and changing the speed of blood flow;
- gas exchange - absorbs oxygen and releases carbon dioxide.
Skin as a sense organ
Touch is our ability to interact with the world around us through tactile sensations. On every millimeter of the skin there are receptors that turn the influence of external stimuli into a nerve impulse. This implies another important function of the skin - receptor, which is represented by:
- feeling of touch and pressure;
- feeling cold and warm;
- feeling pain.
Types of touch:
- active - feeling an object with the help of any part of the body (hold an apple in your hand or walk barefoot on the grass);
- passive - involuntary sensation of the object (the cat lies on our knees);
- instrumental - the feeling of an object with the help of an auxiliary object (inherent in blind people with a cane).
Final summary
So, human skin is the result of the evolution of integuments (from invertebrates to mammals). The skin is made up of three layers: the hypodermis (fatty tissue), the dermis (the actual skin) and the epidermis (surface protection). The epidermis is a layer capable of the regeneration process and having appendages: sweat and sebaceous glands, nails and hair. In the question of what is the main function of the skin, first of all, it is necessary to mention the protective one. Additional functions: gas exchange, cleaning, temperature control. Do not forget also that the skin is a sensory organ that performs a separate function of the skin - a receptor, thanks to which we can feel objects, feel pain and temperature.
