1 вопрос На русском
жүктеу/скачать 119,35 Kb.
|
СРО Химия
| На английском
Heterogeneous processes are important in the life processes of the body and allow us to understand the mechanism of formation of bone tissue substance, the effect of calcium buffer, the physicochemical basis for the development of such diseases as urolithiasis, rickets, gout, etc., as well as to substantiate a number of therapeutic measures and diagnostic methods. research. A deep understanding of the patterns of formation and dissolution of sparingly soluble salts in the human body is necessary for a future doctor. In the human body, bone formation is the most important heterogeneous process involving inorganic compounds. The main mineral component of bone tissue is calcium hydroxophosphate Ca5(PO4)3OH [1]. Along with crystalline calcium hydroxophosphate, bone tissue contains amorphous calcium phosphate Ca3(PO4)2, which gives flexibility to bone tissue, the content of which decreases with age. The formation of Ca5(PO4)3OH is facilitated by a slightly alkaline environment (рН≈8.3); in a more acidic environment, the process of demineralization occurs. During the formation of the bone tissue of the tooth, along with calcium hydroxophosphate, calcium fluoride phosphate Ca5 (PO4) 3F, a less soluble and mechanically stronger compound, is formed in the tooth enamel. In addition, an increased concentration of calcium ions in saliva (an ion of the same name) leads to its stabilization. The cause of caries is the dissolution of calcium hydroxophosphate under the action of acids contained in saliva. Since Ca5(PO4)3F is more resistant to acids, it is necessary to use toothpastes containing Ca2+ and F– ions, which stabilize tooth enamel. The bone tissue of an adult is in a stationary state. The daily exchange of calcium in bone tissue is 0.7-0.8 g. A complete restructuring of bone tissue is carried out approximately every 10 years. Maintaining the concentration of calcium ions in the body at a constant level (2.25-2.75 mmol / l) is provided by bone tissue and blood plasma. This system should be considered as a calcium buffer, the functioning of which is regulated by hormones. With a decrease in the concentration of calcium ions in the blood, resorption (resorption) of bone tissue is activated by special cells - osteoclasts. At the same time, organic acids are formed in the intercellular substance, mainly lactic, which contribute to the dissolution of calcium phosphates. With an increase in the concentration of calcium ions, the number of osteoclasts decreases, bone resorption is inhibited, and mineralization is activated. The mechanism of heterogeneous processes also underlies a number of pathological conditions. In addition to phosphates, calcium ions form other poorly soluble compounds under the conditions of the body. For example, the formation of calcium carbonate CaCO30 is the cause of atherosclerotic calcification. The development of urolithiasis is facilitated by the formation of calcium oxalate CaC2O4, magnesium ammonium phosphate NH4MgPO4, calcium carbonate phosphate Ca10(PO4)6CO3 H2O, uric acid and its salts. Bone tissue is capable of isomorphic substitution of ions of its components in the nodes of the crystal lattice for other components. The phenomenon of isomorphism can cause a number of pathologies. Thus, the competitive replacement of calcium with strontium, which forms the less soluble compound Sr5(PO4)3OH, leads to the development of strontium rickets, which causes bone fragility. Substitution of calcium for beryllium causes berrilosis - softening of the bones. Heterogeneous processes are also used to correct some pathological conditions. For example, precipitation reactions are used in case of poisoning with oxalic acid or its salts, introducing a solution of CaCl2 as an antidote, in case of poisoning with barium salts, the stomach is washed with a solution of MgSO4. Precipitation dissolution reactions are used less frequently. For example, the treatment of gout and urolithiasis is carried out with salts of citric acid, tartaric acid and its salts, lithium salts. Some poorly soluble compounds are used in pharmacotherapy. Their action is based on the combination of heterogeneous and protolytic equilibria. Aluminum hydroxide, which forms its basis, is an antacid. The dissolution of aluminum hydroxide stops at pH=4, which prevents complete neutralization of gastric contents. In this case, the digestive activity decreases, but does not stop. The undissolved part of Al(OH)3 has an enveloping and adsorbing effect. жүктеу/скачать 119,35 Kb. Достарыңызбен бөлісу:
|