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- Human skin analysis
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Human skin analysis
Human skin is a very complicated structure, constructed from various types of chemicals. It is an integrated system with interacting with each other chemical components. Human skin in 69-73% of water.
Different layers of the skin vary considerably in its content: the share of the epidermis is about 10%, papillary layer – 71-72%. net dermis – about 61%. Normal cells activity is under constant ionic composition and pH of body fluids. In the water, readily soluble chemical compounds containing polar groups and capable of entering into the dipole-dipole interactions with water molecules or form with hydrogen bonds (-OH,-NH, C = 0): non-polar hydrocarbon molecules poorly or not soluble in it.
On the mineral science components of the skin accounts for between 0.7 to 1% of dry weight of the skin, and subcutaneous tissue – about 0,5% of its dry weight. The skin is an important depot of cations – sodium, potassium, calcium and magnesium. Sodium is the major extracellular cation in the human body. However, potassium ions, it participates in the regulation of water-electrolyte and acid-base balance. In the skin of sodium contained mainly in the intercellular space, and potassium (75%>) – in the cell cytoplasm. Calcium is contained mainly in the dermis and is involved in the activation of synthesis of prostaglandins. Magnesium also is an intracellular cation, they are the richest in the epidermis. Magnesium is involved in the activation of kinases in phosphorylation reactions.
Important role in biological systems of the body are phosphates. Phosphorus is in the cell mainly in the form of organic compounds – phosphoric, nucleoproteins, adenosine phosphates, etc. Sulfur is part of the cysteine and methionine – amino acids involved in the formation of keratin, and is contained mainly in the stratum corneum of the skin, hair and nails.
For dermatology great interest elements such as copper, zinc and iron that make up enzymes, vitamins, and play the role of activators of biological processes. For example, a tyrosinase, copper is involved in the synthesis of melanin, a lysyl oxidase – the exchange of elastin and collagen, through tioloksidazu – in the process of keratinization, iron is an integral part of hemoglobin, myoglobin, peroxidase and cytochrome providing cellular respiration.
The most important chemical component of the skin is a protein – a polypeptide formed by the condensation of amino acids. In the skin contains the structural proteins: collagen, retikulin, elastin and keratin. The main structural protein of skin collagen is contained mainly in the dermis (about 70% devoid of water of the skin), and retikulin and elastin contained in the skin in much smaller quantities, form the basis of the reticular and elastic fibers of the dermis, the connective tissue membranes of the sebaceous and sweat glands, are of the hair follicles. Keratin is the basis of the stratum corneum. Its synthesis begins in the basal keratinocytes in the form prekeratina, which has a lower molecular weight compared with mature keratin. He has no intra-and mezhtsepochechnyh disulfide bonds, giving the molecules of keratin strength and insolubility. In the lower ranks of the stratum corneum prekeratin under the influence of specific enzymes into a mature keratin. In this case between the individual molecules within them formed disulfide bonds at the expense of the keratin acquires strength and loses solubility. Special protein – filagrin – causes the aggregation of keratin filaments. As the synthesis filagrin keratogialinovyh accumulates in the form of granules, and there are up to as long as tightly packed keratin stabilizes strong disulfide bonds. Then filagrin in korneotsitah decomposes to free amino acids.
Contents of the decay products of protein (urea, uric acid, amino acids, ammonia, etc.) in the skin, almost 3 times higher than their levels in the blood, it becomes even higher in the pathologically changed skin areas with the prevalence of decay processes. Much of the skin cells, like other cells of the body (especially their nuclei), are nucleoproteins and nucleic acids (DNA, RNA). In the skin of DNA and RNA are contained mainly in the epidermis.
The share of the skin accounts for about 20% of the total carbohydrate metabolism. In the epidermis the concentration of glucose is around 30-60 mg%, and glycogen – 70-80 mg%. Despite the small number (approximately 0,1%), glycogen is an important source of energy for the processes of cell division and keratinization. In the skin of adult human glycogen is contained mainly in the thorny and basal layers of the epidermis. Glycosaminoglycans (mukopolisaharily), having a high viscosity, promote cells binding together. Structure and functions of the skin play a major role acidic mucopolysaccharides: hyaluronic, chondroitinsulphuric acid and heparin. When depolymerization of mucopolysaccharides (eg, with an increase in hyaluronidase activity) reduces the viscosity of gels formed by them, and thereby increases the permeability of the skin tissues to microbes and various toxic products. Heparin is formed in the skin and accumulates in fat cells and plays an important role in the regulation of microcirculatory processes.
The skin is rich in proteoglycans, consisting of polysaccharide (95%) and protein (5%) components. As polyanions, they bind water and cations, forming the main substance of connective tissue.
As in the skin, and on its surface contains a variety of lipids. Lipids of the epidermis contain 20% of free fatty acids, triglycerides 17%, 6% mono-and diglycerides, 16% cholesterol. The bulk of the subcutaneous adipose tissue are neutral fats. They dominated most low-melting triglycerides – triolein (70%), in connection with which human fat has the lowest melting point.
Other lipids (sterols, steroids and phospholipids) are contained in the cells of the epidermis and connective tissue in the walls of blood vessels and in smooth muscles and especially in the secretion of sebaceous glands. The skin surface lipids are mixed to form sebum. The fat content increases after puberty and decreases with age.
The skin contains a large number of enzymes, the most important of which are amylase, phosphorylase, aldolase, lactic acid dehydrogenase, succinic acid dehydrogenase, cytochrome oxidase, transaminase, arginase, lipase, tyrosinase, etc.
Human skin contains a large number of antigens (some types of collagen, nuclear antigens, antigens of endothelial cells, fibroblasts and structure, etc.). In common diseases and skin diseases in relation to them can produce antibodies or autoantibodies. Their detection is used for diagnosis and prognosis of the disease.