The skin is the largest human organ. It covers our approximately. 2 square meters of surface and weighing about 3 kg. The skin has a number of functions, including overall protection of the organism is the most important.
The mechanical protection is the skin as a quick healing layer, which skærmer body's internal parts against knocks and scrapes. The skin contains a lot of sensory cells that make us, for example. reflex withdrawing hand to us when we are touching something hot or sharp, to avoid more damage to the body.
The skin is also part of the body's immune system, using its high density physical keeps bacteria and other harmful micro-organisms and substances out of the body. In addition, the skin is waterproof, which is important to prevent water evaporation. Man consists predominantly of water and would quickly become dehydrated if the skin is not held back the water.
The great danger of serious damage to the skin (eg. Major burns) is that infections and fluid evaporation have free rein through the broken skin.
The skin (cutis) is constructed of two layers. The top, visible layer of skin called the epidermis or. Under the leather is the skin or dermis, which is thicker than the skin. In these two films can be found under the skin, subcutis, which form a layer of insulating and cushioning fat.
More than skin consists of two layers - a layer of very dead, forhornede cells and internally a vibrant, active cell layer. There is a very rapid turnover of cells.
The vast majority of the cells is of the type called pladeepithel. They formed all the time in the live portion of the skin and are then ejected from the surface, where again formation of new cells under them. As epithel cells are approaching the skin surface, they are filled up by a hard substance, keratin, which they die. This process is called forhorning and outer layer of skin called therefore horn layer. (Keratin is also the substance that makes hair and nails hard).
Hudbarriere and color
The living cells in the skin produces a range of fats, which attaches itself between the horn cells, forming an almost perfectly impermeable barrier. Hudbarrieren prevents partly foreign microorganisms in free to invade the body and prevents the water to evaporate from the deeper layers of skin, thus drying of the skin (see Skin Care) and dehydration.
More than Skin live layer contains pigment cells (melanocytes). The dye produces melanin, which protects the underlying læderhud from harmful UV rays from the sun. It is melanin, which gives the skin brown color after exposure to the sun.
Cell Turnover in the epidermis
Skin Over dead horn cells eventually wear out of because of the friction that skin exposed. In this way keeps the skin over a roughly constant thickness (less than one millimeter). Abrasion occurs mostly when we go and work with your hands, but also as a result of all movements and tear of clothing. A large proportion of ordinary house-dust actually consists of these dead cells!
It takes on average two months before a newly-formed skin cells when the skin surface and slides by. The body parts which are exposed to greater wear and tear, has a thicker surface, and therefore takes the turnover of cells in the skin of these body longer. Some skin diseases caused by disturbances in the turnover of skin cells. For example, on Psoriasis, there is an accumulation of dead skin cells on the outside, because the formation of new cells in the skin deeper part is unusually large.
Leather Skin is thickest layer of skin. It is first and foremost a bindevævslag, which gives skin its strength and elasticity. Then there are the leather skin many specialized tissues, for example. follicles, sweat glands, sebaceous glands and sensory cells.
Leather skin cell is much more poor than the skin. There is most bindevævsceller (fibroblasts). These cells produce fibers with different characteristics. The dermis is thus plenty of fiber materials of collagen and elastin. The collagen fibers are family members of those particular cartilage is structured and gives the skin its strength. Elastinfibrene is, as its name implies, elastic and gives the skin its firm and elastic. In addition to fiber structures are also other molecules, which among
When the skin is aging and creating wrinkles, it is mainly because Volume woven into dermis becomes more sparingly and the skin becomes thinner and loses its elasticity and water retention (see Age Changes in the skin).
As noted above, the dermis also a lot of special structures. There are many glands, which produce tallow and sweat. Their ducts extends up through the epidermis and culminates in the pores on the surface. If the sebaceous glands to produce (as in puberty) or pores are stopped, it can lead to infection of the glands that are seen as Acne (acne, impure skin). The follicles are in the tough læderhud, and therefore sits hair as fast as they do!
Finally, the dermis rich in sensory cells. These specialized cells are directly related to the nervous system and detects pressure and touch, cold and heat and pain from skin to the spinal cord and brain. Some diseases occur when, for example. a virus using the long nerve cells to spread to the skin. This applies for example. Cold and Shingles, which are both due to a herpes virus (respectively herpes simplex and herpes zoster).