EXCRETION (lat. excretum allocated) — set of processes of removal from an organism of end products of a metabolism, and also connections, alien and harmful to an organism. The substances which are emitted from an organism to the environment by E., received the name of ekskret.
AA. is a component of processes of a metabolism (see the Metabolism and energy) and it is directed to maintenance of a homeostasis (see). Various bodies and body tissues, first of all kidneys, the alimentary system, lungs, skin participate in excretion.
In the course of metabolism of proteins and nucleinic to - t are formed various products of a nitrogen metabolism (see), to-rye are allocated with kidneys (see Kidneys, physiology). Depending on type of an end product of a nitrogen metabolism distinguish ammoniotelic organisms, to-rye excrete preferential ammonia; the urikotelichesky organisms emitting nitrogen, hl. obr. in the form of uric to - you and similar to it connections; urotelichesky organisms (the person treats them), at to-rykh a key product of a nitrogen metabolism urea is (see). At the person concentration of urea in blood makes 3 — 7 mmol/l, daily urine contains 20 — 35 g (330 — 580 mmol) of urea. In final urine of the person find over 30 various substances: creatinine (see Creatine), uric acid (see), various guanidines (see), etc. Activity of kidneys provides constancy of osmotic pressure (see), a dynamic equilibrium between ingress of water and salts in an organism and their excretion (see the Water salt metabolism). AA. kidneys it is important also in ensuring constancy of pH of blood (see Acid-base equilibrium).
Digestive glands excrete in went. - kish. a path a significant amount of water, various nitrogenous and medicinal substances that in defined degrees matches with excretory function of kidneys. AA. the digestive device it is closely connected with processes of secretion (see) and an intermediate metabolism. AA. it is inherent in all digestive glands, but each of them has a swap of feature. By means of sialadens and mucous membranes of an oral cavity toxic medicinal agents are removed from blood (mercury, bismuth, bromic and iodide drugs, morphine, etc.). With saliva urea and the ammonia which is formed of it are emitted in significant amounts. AA. sialadens of acids, the bases, waters, sugars promotes maintenance in an organism of the major homeostatic constants, acid-base equilibrium (see Salivation).
It is exclusive is important in E. a role of a stomach (see). The gastric juice contains a number of end products of a metabolism (urea, uric to - that. ammonia). Glands of a stomach participate in E. medicinal and toxic agents (mercury, morphine, iodine. bromine, quinine, salicylates etc.), dyes (neutral red, indigo carmine, etc.).
The liver (see) also takes part in excretion of various substances. Existence in bile (see) a large number of the same connections, as in urine, and ability of a liver to emit the substances connected with krupnomolekulyarny not water soluble proteins give the grounds to many researchers to consider a liver preferential excretory body. With bile urea, ammonia, arsenic, silver salts, nickel, aluminum, benz (and) pyrene, thyroxine (see), calcium, phosphorus, etc. are emitted. The liver also participates in release of an organism from products of exchange of hemoglobin (see).
With pancreatic juice in went. - kish. the path is allocated urea, uric to - that. mercury, iron, bromine, iodine. paints, etc. Intestinal glands excrete compounds of mercury, silver, iron and other metals. urea, lactic acid (see), paints.
The role E is especially evident. the alimentary system at decrease or disturbance of a functional condition of the main excretory body — kidneys. However and in normal conditions E. and the intermediate metabolism which is carried out went. - kish. a path, favor to activity of kidneys protecting them from an overstrain during the providing excretion.
In the course of oxidation of proteins, fats and carbohydrates in an organism carbon dioxide is formed. The main part it is removed by lungs (see Breath). Along with carbon dioxide gas lungs bring out of an organism water I nek-ry volatile substances (e.g., vapors of ether and chloroform at an anesthesia, vapors of alcohol at intoxication) that allows to consider lungs the body performing functions E.
Excretory function of skin is predetermined by its participation in water, salt and other exchange processes (see Skin, physiology). Normal through skin about one third of the emitted water is brought out of an organism, and at high temperature of the environment much more (see Sweating). AA. skin are substantially tied with activity of sweat and sebaceous glands. With then (see Sweat) chlorides, sodium, potassium, calcium, lipids and other substances are excreted. Under certain conditions E. calcium through skin can exceed considerably its allocation with urine. A considerable part of not saponifiable fraction of skin fat (to 40 — 55% of its weight) make aliphatic hydrocarbon squalene (see) and cholesterol (see). Detection in not saponifiable fraction of skin fat 17 of ketosteroids, glucosteroids, products of exchange of sex hormones, adrenal hormones and vitamins allows to consider skin excretory body for steroids (see), their intermediate products, a number of hormones, vitamins and enzymes.
In a complete organism all bodies and fabrics which are carrying out E., interact, providing constancy of internal environment, organism (see). It is reached by coordination of work of the functional systems directed to maintenance of separate homeostatic indicators, difficult and various neuro and humoral mechanisms of their providing. In cases of reversible functional disturbances of the bodies and fabrics participating in E., there is partial compensation of excretory functions in an organism. However full compensation at heavy disturbances of the main excretory body — kidneys — does not happen.
Dli of studying E. use various a wedge. the methods offered for assessment of function of kidneys, the alimentary system, lungs, skin.
Bibliography: Kalantayevskaya K. A. Morphology and physiology of skin of the person, Kiev, 1972; Skin. (A structure, function, the general pathology and therapy), under the editorship of. A. M. Chernukh and E. P. Frolov, M., 1982; Natochin Yu. V. Fundamentals of physiology of a kidney, L., 1982; Ryabov S. I. and Kozhevnikov A. D. Kidneys and metabolism, L., 1980; physiology of digestion, under the editorship of A. V. Solovyov, page 587, L., 1974; Physiology of a kidney, under the editorship of Yu. V. Natochin, L., 1972.
V. G. Zilov.