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WATER-ELECTROLYTE EXCHANGE
Functions of water in the organism 1. Plastic material. 2. Universal solvent owing to which a transfer of active substances is performed in vertical and horizontal directions (heart — kidneys, vessels — interstitial space — vessels). 3. The most used chemical reagent in chemical reactions of cells.
common water — 60% of body weight, of them:
Extracellular section is subdivided into the intravascular and interstitial ones. A decisive property of the extracellular section is a constancy of concentration of different substances dissolved in it that was laid down as the basis of teachings of homeostasis, the essence of which lies in the maintenance of physiologic norm in the organism. Intravascular section is the most mobile sector of active circulation. Protein content is 2-3 times higher than in the interstitial fluid. In connection with this a share of pure water makes up 93% of the volume. Interstitial section — water takes up the space between capillary and cellular membranes. This section is a shock absorber of strong hydroosmotic disturbances and active sector of intra- and extracellular osmoregulation. A continously moving in two directions — by absorption and excretion, controlled by requirements of tissues, extracellular medium maintains a quantitative and qualitative stability. This stability includes hydroosmotic, acid-alkaline and thermal equilibrium. Extracellular space represents a medium where the organism lives. Intracellular section — contains water in three forms: constitution water of protoplasm (stationary), water of attraction on the surface of colloid micellas (low mobile) and water of capillarity (the most mobile). A continuous exchange takes place between them. Cellular water is differently distributed in various tissues, in which connection the most hydrophilic tissues are the most vulnerable in relation to water exchange. So, a cerebral cortex contains 85% water, a white substance of the brain — 70%, pulmonary tissue — 82%, kidneys — 80%, muscles — 75%, liver — 70%, connective tissue — 60%, fat — 30%, bones — 25%, teeth— 10%. Water of capillarity makes up a great part in the cells. A part of cellular water is formed as a result of metabolic processes of combustion, so-called endogenic water (300-350 ml/day). Of the factors retaining water in three sections, the main role is played by electrolytes — substances dissociating with formation of cations and anions. A sum of anions in every section is equal to the sum of cations owing to this the electric neutrality is ensured. A deviation from this rule leads to AAB disorders. Total number of meq/1: — in plasma — 310, — in interstitial fluid — 290, — in cellular fluid — 340. A predominant cation in the extracellular fluid is Na+ and in the intracellular fluid — K+, a predominant anion in the extracellular fluid — Cl~, and in the cells — P". Дата добавления: 2015-02-05 | Просмотры: 725 | Нарушение авторских прав |
