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Beautiful and well-groomed skin can be a real decoration, which is why it is usually assessed in terms of aesthetics. Meanwhile, it is an important organ that performs important protective functions in our body. Find out how the skin is built.
Humanskinhas remarkable properties. With a surface area of approx. 2 m2and 1-4 mm thick, it is one of our largest organs. Resistant to heat and frost. It is not afraid of water, as well as acids and bases, as long as they do not have too high concentrations. It remains soft, flexible and resistant to stretching even when it is exposed to unfavorable weather conditions for many years or dried in air-conditioned interiors. Its durability makes it perfectly protects internal tissues and organs. Using a complex system of sensors, it provides the brain with detailed information about its surroundings and ensures thatbodyadjusts to the conditions outside.
Three layers of skin
Its structure is apparently quite simple. The skin consists of three layers of different thickness. The outer one isthe epidermis , under which there is the dermis lined from the bottom with the last layer - the subcutaneous tissue. Each layer contains layers of very diverse cells. Revealing its secrets, the structure of the skin turns out to be an elaborate and complicated creation. It is covered with a lipid coat from the outside. It consists of a water-oil suspension and protein (keratin) molecules produced by keranocytes, the basic cells of the epidermis. They are produced at the deepest level, in the basal layer of the epidermis, and they flatten and die over time. Those that are located uppermost in the stratum corneum are constantly exfoliating, revealing subsequent layers. As long as we are young, this process is short, about 24 days, and the stratum corneum is quite thin. That is why the skin has a he althy, nice shade, it is elastic and radiant.
With age, the keratinization process is significantly longer, even up to 35 days. The skin loses its glow, and the thicker stratum corneum inhibits the absorption of, for example, creams that stop working, and the secretion of sweat and sebum. Deep blackheads appear, the skin becomes dry and not very elastic. Excessive or incorrect keratinization causes many skin diseases, such as ichthyosis and psoriasis.
The cells of the epidermis are also found in the environmentthe warts of the hair and around the back and sides of the nail plates. Thanks to the sweat and sebaceous glands, along with skin secretions - sweat and sebum - harmful metabolic products are removed and the skin can function as a body thermostat.
Flexible leather interior
The dermis is made of compact connective tissue. Characteristic of its outer layer, called papillary, are papillae (protrusions) that contain capillary loops or nerve and touch bodies. This is our touch organ. These characteristic prominences constitute the boundary between the epidermis and the skin. The inner layer consists mainly of several types of collagen fibers produced by fibroblasts and fibrocytes. These fibers form a flexible network with thick meshes. It acts as a skin scaffold. That is why, when these fibers begin to disappear around the age of 40, the first irreversible wrinkles appear in the most weary places, e.g. on the face, waist, hands.
Apart from collagen fibers, the dermis also contains fibers resilient (their origin and function are not yet fully understood; they probably make the skin supple) and individual blood cells and immune cells. At this level, in certain areas of the body, such as around the nipples and areola, and in the scrotum, there are also clusters of smooth muscles that enhance our erotic sensations.
The skin registers touch and pain
Under the dermis, there is the subcutaneous tissue, which consists of fatty lobules. They are separated by compact connective tissue with collagen fibers, called type III collagen. Between them are blood vessels and nerve endings.
The skin has a very branched nerve network. Its many ends are irregularly distributed all over the body. They entangle the hair follicles, sweat and sebaceous glands. Their task is to register the sensations of touch and pain. They have the ability to feel stimuli in a radius of 1 to 12 mm. Touch receptors include, among others Merkel tactile meniscus, responsible for the exact location of the stimulus, and Meissner tactile bodies. The more densely they are placed, the greater our sensitivity to pressure. In this respect, however, the hairless areas, such as the fingertips, lips and the tip of the nose, are unattainable, and the least sensitive - the arms, thighs and the back. If you want to cause a reaction in the skin on the tip of the nose, you just need to pinch it gently (with a force of just 2 g / mm2). But in order to have a similar effect on the skin of the arms or thighs, you need to squeeze these places as much as 20 times harder. The receptors transmit the received stimuli to the brain (or rather tothalamus and the sensory cortex), thus providing information about the sensory experience. Simply put, we feel touch, temperature and pain through our skin. This manifests itself in different ways.
In the brain, signals are analyzed. For example, the impression of humidity is created by stimulating the touch and cold receptors. On their basis, the brain decides on the degree of vascular contractility and the release of histamine, which is mediated, among others, by in the development of inflammation. The receptors responsible for tactile sensations also inform about the sensation of itching, temperature changes and pain. Its appearance is usually the result of tissue damage. The increasing strength of the stimulus causes the feeling of touch, pressure, heat or cold to turn into distinct pain. The mechanism of its perception is chemical. This is because mediators are released from damaged tissues - chemical compounds which, by affecting nerve endings, trigger reactions in them that lead to the creation of an electrical impulse.
Skin colors and tones
The color of our skin depends on melanocytes, cells derived from the nervous system. The differences in the color of the skin in representatives of different races is a consequence of differences in the number of melanocytes in the epidermis, and especially in the degree of their activity. Located between the cells of the reproductive layer of the epidermis, melanocytes produce and store the pigment - melanin. It is injected through their long and branched plasma projections into the cells of the epidermis. Melanin protects the genetic material of epidermal cells against the harmful effects of ultraviolet rays. However, the most intense pigmentation is not on the exposed parts of the body, but on the covered, usually external genitalia, and also around the nipples.
ImportantAny deeper wound that reaches at least the dermis leaves a thickening called a scar. Compact, poorly vascularized connective tissue is produced at the site of damage. There are hypertrophic and atrophic scars. The tendency to create unsightly, overgrown scars is usually an individual skin trait. The skin scar is not hairy because there are no hair follicles in it.
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