Remember Luke Besson’s wonderful movie The Fifth Element? At the beginning of the film, scientists from a futuristic laboratory recreated the human body from preserved cells. After restoration of bone tissue and muscles, the scientist says:
The last stage. Irradiation of cells with ultraviolet light stimulates a protective reaction of the body, that is, the skin grows.
Despite the fact that the film belongs to the category of fiction, the scientist did not lie, and the scriptwriters paid special attention to this important process. So what are the functions of the skin and what is its value to the human body? Let's figure it 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 living conditions and environmental factors. According to the theory of evolution, the process of formation of the skin that we have today happened like this:
- only invertebrates lived in the seas and oceans: sponges and jellyfish having 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;
- the first vertebrates that came to land found another layer of cover, producing keratin proteins;
- keratin proteins were transformed into an insulating layer, which appeared in the form of skin.
Vertebrates living on land were exposed to ultraviolet rays (the sun), which played an important role in the evolutionary processes of skin appearance. This was a reference from the film.
Structure
The skin, like any other organ, is very complicated: scientific articles on several tens of pages have been written on this subject. Therefore, we will try to understand without the subtleties of scientific topics, in simple and understandable words for everyone.
The skin consists of three layers: the epidermis (upper), dermis (middle) and hypodermis (lower).
Hypodermis is the fat layer, or, roughly speaking, fat. All the bars and waffles that we ate late at night are stored here. The thickness of the hypodermis varies in the range (depending on the part of the body) of 0.2-6 cm, obesity increases these numbers by 2-3 times. Hypoderma 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 fatty 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 necessary moisture from fatty tissue and blood, which means that in the pursuit of youth, you should eat right first and not buy expensive cream. The basis of the dermis is collagen, elastin and proteoglycan. The first gives the skin elasticity, the second - elasticity, the third holds water.
And finally, the top layer is the epidermis, represented by just a few layers of cells. The main task of the epidermis is to protect against pathogenic microorganisms. Between the epidermis and dermis there is a basement membrane that regulates the exchange processes between the layers and is an additional protective barrier.
Epidermal appendages
The upper layer of the skin (epidermis) is supplemented with appendages:
- Sweat glands are apparently involved in sweat production. Mostly located in the axillary and inguinal areas, as well as on the face, palms, feet.
- The sebaceous glands gave the person such nuisance as acne. But sebum is produced for a reason: it softens the skin and serves as a grease for hair. For this reason, the sebaceous glands are located next to the hair follicles.
- Hair is found on the entire surface of the skin, with the exception of the palms, feet, eyelids, lips and especially sensitive areas of the genitals. The hair on the head protects us from sunstroke or, conversely, from frostbite. But fluffy hair is a vestige and does not play a significant role for modern man.
- Nails are horn 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 around the clock (renewed). This is possible thanks to keratinocytes - cells that are 80% collagen. Keratinocytes nucleate in the depths of the epidermis and within 2-4 weeks reach the upper layer of keratinized cells, and then die. This process is necessary not only for continuous updating, but also for maintaining the optimal thickness of the epidermis due to its protective function.
Skin regeneration is of two types:
- physiological - the natural process of updating the epidermal cells;
- reparative - the healing process as a result of mechanical damage.
Slowing down regeneration processes
With every year of life, the process of epidermal cell renewal slows down, which inevitably leads to the first signs of aging - wrinkles. It is generally believed that the main cause of aging of the skin is its insufficient blood supply, as a result of which a deficiency of nutrients occurs and metabolic processes in the cells slow down. By the age of 25, the body begins to redirect fresh blood flow to 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 updated in 14-28 days, then in a forty-year-old man - in two months.
Human skin functions
Imagine a person without skin. What is this fraught with and what could be the consequences? The pathogenic influence of the world immediately comes to mind. And this is absolutely true! First of all, human skin performs the function of protection, that is, it provides a kind of barrier against pathogenic bacteria and adverse environmental factors. Including protects internal organs from shock and bruises, which is ensured by the softness and mobility of fatty tissue.
Additional skin functions:
- cleansing - removes harmful metabolic products from the body through sweating;
- thermoregulating - maintains the necessary temperature of the body by regulating the intensity of sweating and changes in blood flow velocity;
- gas exchange - absorbs oxygen and emits carbon dioxide.
Skin as a sensory organ
Touch is our ability to interact with the outside world through tactile sensations. Receptors are located on every millimeter of the skin, converting the influence of external stimuli into a nerve impulse. From here follows another important function of the skin - the receptor, which is represented by:
- a sense of touch and pressure;
- feeling of cold and warmth;
- feeling of pain.
Types of touch:
- active - the sensation of an object with the help of any part of the body (we hold an apple in our hands or walk barefoot on the grass);
- passive - an involuntary sensation of an object (a cat lies on our knees);
- instrumental - the sensation of an object with the help of an auxiliary object (inherent in blind people with a cane).
Summary Summary
So, human skin is the result of the evolution of integument (from invertebrates to mammals). The skin consists of three layers: hypodermis (fatty tissue), dermis (skin, in fact) and epidermis (surface protection). The epidermis is a layer capable of regeneration and having appendages: sweat and sebaceous glands, nails and hair. In the question of which skin function is the main, the protective should be mentioned first. Additional functions: gas exchange, cleaning, temperature control. We also do not forget that the skin is a sensory organ that performs a separate function of the skin - the receptor, thanks to which we can sense objects, feel pain and temperature.