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Skin function and structure
Human skin is the largest human organ - its surface covers up to two square meters. At the same time, there is often ignorance about how important it is for our lives. Many see it as a kind of shell that holds the inside of the body together.
It does make the skin too, but it is much more than a "sack" for bones, flesh and internal organs. As a shell, it separates our body from the outside world, protects it from drying out, keeps pathogens out as well as sunlight, fends off both heat and cold.
The "skin filter" can be used medically: creams, oils, lotions healing baths and healing earth applied to the skin, provide the body with well doing substances. Also active ingredients such as hormone patches or nicotine patches are absorbed through them.
contents
- A sense organ
- The skin as a protective shield
- The biggest organ
- Three layers of skin
- How protects the skin?
- Protection inside
- body temperature
- A contact organ
- The color of the skin
- waste
- The surgeon at the entrance
- Greasy or dry
- When does skin look nice??
- The old skin
A sense organ
It is also a sensory organ and makes us feel pain and temperatures. A network of millions of nerve cells ensures that we can sense whether a surface is smooth or rough, hairy or made of plant fibers.
With closed eyes we determine with our fingertips a sugar shaker, a chair or a book. What's more, the nerve cells even tell you whether the sugar shaker is made of glass or ceramic, has a bulbous or cylindrical shape, whether it's a paperback book or a bound edition.
We feel whether the book has a dust jacket and what material it consists of, whether the book contains about one hundred or two hundred pages, how tall the back of the chair is, whether it is made of wood or metal, whether it is a desk chair or a living room chair.
With the senses, we not only grasp whether we touch something, but also what it is. Pain impulses direct the nerves of the outer skin directly into the brain and warn us in this way of dangers and possible injuries.
The skin is the largest human organ and fulfills a variety of vital tasks. (Image: PixieMe / fotolia.com) Other creatures, such as cats or walruses, can feel things with hair in the facial skin many times better than humans, and thus "see" skin to a much greater extent..
The skin cells regulate the temperature of the body. A network of vessels and glands ensures that our body heat remains stable.
This super organ also acts directly on our communication and psyche - usually unconsciously. Shame and anger provide for a stronger circulation and drive us the blush in the face.
If we get scared, we get "goose bumps", we feel aggression, our neck hair bumps, our fingertips twitch with excitement.
The skin as a protective shield
It produces sebum like sweat, creating a coat that protects us from acidity and maintains a pH between 4.5 and 6.9.
The skin protection is not only directed to the outside, but also to the inside: With the sweat she transports the waste of the body to the outside. Conversely, the lipids in the sebum ensure that chemical substances and water are kept away from the body. At the same time, they ensure that the skin remains sufficiently moist.
This shield is vital: if we lose by a fire, 20% or more of our skin tissue, then we can die from it.
The biggest organ
A man of medium height and normal weight is in a skin coat of about two square meters. It is one to two millimeters thick and weighs between three and ten kilograms.
Their color is different for each individual and is due to the amount of blood, the distribution of the pigments and the thickness of the epidermis.
The different skin layers have different functions and are clearly distinguishable from each other. (Image: designua / fotolia.com) Three layers of skin
The skin is divided into the epidermis (epidermis), the dermis (dermis) and the subcutis (subcutis). The epidermis is above all a horny layer. It serves to protect it from the outside, constantly renews itself and drags it to the outside. The dermis consists mainly of connective tissue and contains the important skin glands. Among other things, the sebum is produced here. The subcutis also contains mainly connective tissue, but this is much looser than in the middle layer and interspersed with fatty tissue.
The skin appendages also belong to her. We count hair as well as nails, but also the sweat and sebaceous glands.
How protects the skin?
The epidermis is filled with fats. As a result, the body loses less water, because the fats protect against evaporation. The three skin layers also provide a buffer zone for bumps, bumps or stitches that will not hurt the internal organs. The horny layer and the film on the epidermis are also a natural sunscreen. They reflect and absorb the sunlight. If the rays penetrate deeper, the melanin transforms them into heat. The acid protection in sweat and sebum prevents bacteria and fungi.
Thus, the sources of some diseases are already named: In too strong sunlight, horny layer, skin film and melanin can no longer absorb the rays; If the acid protection is damaged or fungi multiply like bacteria too much, then pathogens can invade.
Protection inside
The skin protects the body's interior by making antibodies. The epidermis activates the immune system and the body transports blood and lymph into the affected area - everyone knows this from their own skin when they redden and warm themselves around a wound.
The rash in infections such as measles, rubella or scarlet fever is not a symptom of the disease in the narrow sense, but shows on the contrary how the immune system fights off the disease.
body temperature
Warm-blooded animals depend on a constant body temperature. The skin plays a crucial role. The cutaneous vessels contract so that the body does not give off too much heat. That's why we have "goosebumps" when we freeze. The muscles on the hair follicles contract and the hair straightens.
Conversely, it also protects against overheating. If the heat builds up in the body, for example during physical exertion or great sun heat, then the vessels expand and more heat can leave the body.
Their function as heat filters can only fulfill them to a certain extent. To expand this frame, people wrap themselves in an "artificial skin", the clothes. This allows us to survive outside the (outdoor) temperatures that control our skin.
The extent to which we absorb or release heat through them differs from individual to individual, and has to do with genetic differences and skin color. People from cold climates generally have a higher cold tolerance than people from tropical regions because their skin absorbs more heat and gives off less heat. The heat absorption and delivery can also be trained.
A contact organ
The vernacular refers to with phrases such as "that gets under my skin" or "I get it skin swap" the skin as a seismometer for the psyche. In fact, it is not only a protection from the outside world, but also an organ to connect with the environment.
In the dermis are the pain receptors, in the subcutaneous the receptors for pressure. Especially on the face, on the lips, the chin, the nose, the ear cups and the earlobes, the thermoreceptors collect. We have nearly ten times as many receptors for cold as for heat. It is no coincidence that these are mainly found in the described areas of the head: Lips, earlobes and the tip of the nose are the first parts of the body to die from excessive cold - the receptors there warn the brain of this danger.
In the dermis are also receptors that indicate the stretching of the skin.
The receptors for the sense of touch are found in hairless parts, especially in the external genitals, the anus, the nipples, the tongue, the fingertips and the lip. The highest concentration of nerve cells in men has the foreskin of the penis. Again, it is no coincidence that the tactile receptors are in these places: With the fingertips we feel all kinds of objects, the anus we took early was whether harmful foreign bodies penetrate into the body, as well with the lips and the tongue.
For example, if we feel the tiny barbs in the shell of a fruit on our lips, it protects us from eating that fruit and possibly damaging the inside of the body. In the sexual organs, the increased sensitivity through touch promotes sexual arousal.
Excessive sun exposure causes the skin to react with sunburn. This shows the different skin types with different sensitivity to the sun's rays. The evolutionary development of the various skin types probably goes back to the different strong sunlight. (Image: jivimages / fotolia.com) The color of the skin
The skin color is not only different from individual to individual, but also shows itself clearly in different phenotypes of human groups. These differences promoted the pseudo-scientific theories of human races that pursued the primary goal of glorifying or depreciating humans of these supposed "races." Modern biology, however, shows that the color of the skin is primarily a result of adapting to sunlight and says virtually nothing to classify groups of people.
In 2003, George Chaplin and Nina G. Jablonski posed the thesis that humans' black and white skin was an adaptation to too much and too little sun. This would have been a balancing act. UV rays could be devastating to the naked skin cells, and reddish brown to black melanins are a natural sunscreen that prevents skin cancer. Particularly skin cancer endangered people with fair skin in regions with strong sunlight such as Anglo Australians.
According to the researchers, dark skin was created to protect the folic acid in the body from UV radiation. In the sun-poor north, however, hardly any UV-B penetrated her anyway. But that brought no advantage, but a problem with it. Although UV-B rays are dangerous, they are also vital because they trigger the synthesis of vitamin D and are therefore of fundamental importance for calcium and phosphate metabolism, which in turn controls bone structure.
So, the skin color in the northern latitudes needed to get light enough to absorb enough UV-B rays for people to produce vitamin D. Without vitamin D, the body can not absorb calcium from the gut that makes up the bones and the skeleton can not develop normally. Without calcium, the immune system also breaks down.
These relationships have been further underpinned by Michael Hollick of the University of Boston (Massachusetts) and his colleagues over the last two decades through their medical studies. They also showed that sunlight at higher latitudes in winter is insufficient for vitamin D production because too little UVB radiation reaches the skin cells. That's why people in the far north never really turned brown. Because her skin should always catch as much sun as possible. In mid-latitudes, however, people would turn dark in the summer, and in winter their skin would turn a pale color to save little sunlight at this time of the year. In the summer they are protected by their dark skin from too strong sun. In the tropics, however, the radiation is so strong that even with protected pigments enough vitamin D is produced.
Although Inuit in Alaska, Greenland and northern Canada have a darker skin, but only about 5000 years ago immigrated to the Arctic and on the other they had made themselves largely independent of the sun: Traditionally, the Inuit ate extremely high-fat marine fish and thus the food the highest levels of vitamin D In Africa, the Khoisan, the Bushmen of southern Africa, have a much lighter complexion than the Bantu people near the equator, which, according to Chaplin and Jablonski, is probably due to adaptation to lower UV radiation in South Africa.
Today, people often do not adapt fast enough to the sun in a new home, according to Chaplin and Jablonski. This usually happens out of ignorance. Many Indians who came to Britain as citizens of the Commonwealth suffered from rickets and other vitamin D deficiency symptoms in northern England and Scotland.
The skin is also involved in the disposal of "waste products" of the organism via the sweat delivery. (Image: Jürgen Fälchle / fotolia.com) waste
Not only does it provide vitamin D, it also disposes of sodium chloride on sweat. However, like so much in evolution, it does not fulfill this task in the minerals budget. Since sweat also serves to cool the body, we not only lose heat in the heat, but at the same time lose salt and have to recirculate it using, for example, mineral water.
The surgeon at the entrance
It heals wounds so naturally that we hardly worry about how that happens. If a vessel in the middle layer of the skin is damaged, the nerves mediate the injury and platelets fill the affected area. But that's not all: The blood clots and at the same time forms a binder of protein. This fibrin is now used as an adhesive in the wound and hardened there. A protective layer is created and new skin cells form, finally the edges of the wound tighten, and the air dries the initially moist crust.
If the injury is in the lower or dermis, a scar remains. If only the epidermis is injured, everything heals again, the wound goes down to the deeper layers of the skin, a scar can remain behind. Protective cover and sense organ, robust and sensitive - our skin is just a real marvel.
Greasy or dry
Human individuals have either oily or dry skin, or neither. The spectrum is big. Humidity not only varies from individual to individual, but also changes with age and body region. Adolescents, for example, not only have pimples, because their sebaceous glands run at full speed, but also often oily hair and oily skin. But if the sex hormones decrease with age, this process turns around: The skin of old people is dry.
Every skin type has its own problems. If it produces too much sebum, the fat thickens the surface, sebum and sweat clog the pores. This, in turn, allows fungi and bacteria to settle. Too little sebum, however, causes the important protective film of grease and moisture is only incomplete. The result is: Our skin becomes flaky and hypersensitive to cold or dry air. Many people who tend to freeze easily suffer from too-dry skin - often they do not know about this cause.
When does skin look nice??
Skin is considered beautiful if its pores are small, with no scales, pimples or boils on it, if it reflects the light evenly, contains a little fat, shines and wrinkles. Too much fat is just as unaesthetic as dry skin. Evolutionary, our perception is well explained: dandruff, pimples and boils may indicate basic diseases, a dry and dull skin on the one hand to age, secondly also on diseases - or both.
The ideas of beautiful skin are similar in most people: small pores, no dandruff, pimples or boils, even light reflection, light shine and little wrinkles are typical features here. (Image: YakobchukOlena / fotolia.com) The old skin
Age is not a disease; our skin is already aging in young adulthood, which makes it thinner. We can not stop this process, but mitigate it.
Aging means that the papillae change between epidermis and dermis. Blood vessels in these papillae supply the epidermis with nutrients, oxygen and fluid. In young people, these papillae are close to each other and are long - the skin is plump and smooth. In older people, the papillae flatten and become less. The older we get, the less collagen and elastin the body makes, and so the skin loses its elasticity: we get wrinkles. Nutrients and oxygen now only slowly enter the upper skin layer: our skin looks dull. (Dr. Utz Anhalt)