Whether you Can present yourselves in the continuous suit put on a naked body from dense water- and a wind-shelter material? And after all you carry such suit daily is a cotton wool a skin.
The Skin is the greatest body. The total area of a skin of the adult makes about 2 m 2, it weighs of 3 kg - about 5% from body gross weight.
The Thickness of a skin fluctuates from 0,5 mm to more than 5 mm. It is more thin on those sites of a body, which are exposed to friction and pressure influence (for example, an internal surface of a forearm), and more thickly there where it it is more than loading (for example, soles of feet) less.
The Skin consists of two layers. External, epidermis, contains from 20 to 30 layers of dead cages. These cages partially block each other, as a tile that allows a skin to be stretched. Daily from a skin surface sshelushivajutsja thousand dead cages, however it does not lead it istoncheniju as simultaneously there is a continuous process of updating of cages.
Cages of the bottom part epidermisa continuously share. Each new cage is gradually filled with dense protective substance, keratinom. Cages are pushed out in a direction of a surface in process of occurrence under them new. The way upward occupies from three about four weeks, and the cage reaches surfaces already dead. Dead cages sshelushivajutsja from a surface of a body in the form of the smallest, cheshuek. On the average for a life the person "ёсЁрё№трх=" from itself about 18 kg of a dead skin.
The Bottom part epidermisa is sated melanotsitami which develop a pigment the melanin protecting a skin from excessive penetration of ultra-violet radiation. Energy of light is absorbed by melanin, changing its colour for more dark. Thereof, by the way, also there is a sunburn. Melanin is transferred to a surface of a skin and sshelushivaetsja from it together with dead cages therefore sunburn descends. At people with more dark skin the melanin maintenance above. Melanotsity can settle down groups, causing occurrence on a skin of freckles.
the Overheat and cooling
Under epidermisom thicker layer - derma settles down. The top part dermy contains the bound fibres of special proteins - collagen and elastin. They do a skin elastic and elastic.
In derme also there are thousand the smallest blood vessels. When to you hot, these vessels extend, and the blood current through them increases. The additional quantity of blood at a skin surface provides outflow of heat and body cooling. For this reason at the person, kotoro mu hot, the person reddens. When to us it is cold, blood vessels are narrowed, keeping heat, but causing pallor.
The Blood flowing on these smallest vessels, also supplies both layers of a skin with nutrients and carries away the fulfilled products. In case of a cut or other damage of a skin the formed clot of blood covers a wound, having turned to a special crust - a scab. It protects us from microbes and keeps necessary liquids in an organism.
In the top part dermy there are little bodies of Majssnera. These are receptors, vosprini majushchie easy pressure. Slightly more deeply in derme there are little bodies of Ruffini - heat receptors - and little bodies of Krauze cold receptors. At the basis dermy little bodies of Pachini are located, allowing to feel strong pressure. When the nervous terminations register a pain, pressure or temperature change, they send a signal to a brain. In the answer the brain gives to muscles a command to action - for example, to draw aside a hand from a hot cup.
Deeply in derme are potovye glands. They represent the tubes weaved into hard knots and play extremely important role in body temperature regulation. These glands develop sweat - a saltish liquid, which when to us very much hot, through potovye a time acts on a skin surface. Sweat evaporates, helping us to cool down. Glands are capable to develop from 250 to 500 ml of sweat a day. In conditions of a heat and high humidity daily allocation of sweat can reach 2 l.
In our body is to 3 million potovyh glands. Their gross weight makes about 100 They are concentrated mainly in the field of the person, axillary hollows, palms and soles.
The Thin film of sweat covers ledges of a skin relief on fingers, allowing to hold smooth subjects confidently. The skin relief on fingers forms unique - at everyone the drawing.
the Fat skin and hair
In derme hair follicles and sebaceous glands informed with them also settle down. The last develop viscous zhiropodobnoe substance - skin fat which is continuously allocated for a surface, greasing hair and a skin. Without such protection a skin, having dried up, it would start to be shelled, not in a condition to maintain daily loadings and external influences. At some people, especially at youthful age, sebaceous glands vyraba tyvajut too much skin fat that leads to occurrence of eels. In this case follicles are hammered, therefore can occur infitsirovanie bacteria and formation of abscesses.
The muscle lifting hair is connected To each of hair follicles. When to us it is cold or terrible, these muscles are reduced, resulting hair in vertical position. Hair thus pulls behind itself a fabric surrounding it, there is well all an acquaintance "уѕёшэр ъюцр".
Under dermoj the hypodermic fat which is carrying out function softening and teploizolirujushchej of a lining settles down. Simultaneously it is a spare energy source. There is internal - muscles, glands, the basic nerves and blood vessels further. All of them are protected by a live barrier - our skin.