BLOOD CIRCULATION REGIONAL

From Big Medical Encyclopedia

BLOOD CIRCULATION REGIONAL (Latin regio area) — blood circulation in bodies and fabrics (a brain, heart, kidneys, a liver, intestines, skeletal muscles, etc.). Due to the heterogeneous structure of bodies, distinctions in intensity of exchange processes, function, and also in a structure and type of regulation of a tone of blood vessels it is accepted to distinguish also local blood circulation, napr, in white and gray matter of a brain, in a mucous membrane, a submucosa and muscular structures of bodies went. - kish. a path, in cortical and marrow of kidneys etc.

The first data on redistribution of a blood-groove between certain areas of an organism, the level of their blood supply, connected with changes of activity of body, and some features of neurohumoral regulation of vascular areas were received in the middle of 19 century. However the methods of a research used at the same time allowed to judge changes of blood supply of bodies only qualitatively. Only from 40th 20 century thanks to broad use of anticoagulants, artificial perfusion blood of bodies, to electromagnetic and ultrasonic quantitative methods of determination of speed of a blood-groove had an opportunity of systematic studying of active vasomotor reactions, the central, humoral and local regulation of organ blood circulation, and also other parties To. river.

The vascular network of each body has the features of a structure, however in a habit view it can be presented in the form of consistently connected sites: the resistive vessels (including pre-and post-capillary departments), precapillary sphincters, exchange vessels (capillaries) shunting vessels and capacity vessels — generally post-capillary. The arterial vessels performing resistive function have the highest relation of thickness of a muscular wall to the radius of a vessel thanks to what even small reduction of smooth muscle elements can lead to jump of intensity of a blood-groove. Capillaries consist of one layer of endothelial cells (see. Capillaries ). The gleam of capillaries, speed of a blood-groove and pressure in them defining intensity of exchange depend generally on resistance of precapillary and post-capillary vessels (see. Microcirculation ). The capacity department of a vascular bed is of little importance in creation of the general vascular resistance and an essential role in maintenance of hydrostatic pressure in capillaries and the optimum volume of the circulating blood. The shunting vessels provide a feedforward between arterioles and venules, passing capillaries. It is more these vessels in skin where they perform generally function of thermal control. The blood flowing on the shunting vessels does not participate in exchange function; therefore it is necessary to distinguish a total organ blood stream from nutritive, providing a metabolism in fabrics.

Distinguish local and central (neurohumoral) mechanisms of regulation of regional blood circulation. The vessels deprived of nervous and humoral influences keep ability to show resistance to a blood-groove that is caused by the internal activity of unstriated muscles which is especially expressed in precapillary vessels of resistance and precapillary sphincters. For designation of this feature the concept basal, or peripheral, vascular, a tone is entered. The basal tone is high in bodies with a broad range of exchange activity — skeletal muscles, bodies went. - kish. a path, sialadens it is also a little expressed in kidneys.

Blood vessels have property to be narrowed at increase in intravascular pressure and to extend at its reduction (Ostroumov's phenomenon — Beylissa). This myogenetic mechanism functions against the background of the weakening influence on smooth muscle cells of vessels of products of local metabolism of fabrics (the so-called metabolic mechanism). Such phenomena have a talk with myogenetic interaction of the metabolic mechanism To. river as maintenance of a basal tone, autoregulyation, functional and reactive hyperemia. Autoregulyation is a process of maintenance of intensity of a blood-groove and capillary pressure at the certain level at the broad range of fluctuations arterial pressure (see), the most expressed in a brain, kidneys, i.e. in bodies with small mechanical activity. In bodies with high mechanical activity (heart, went. - kish. the path, skeletal muscles) vessels test an extravascular compression, edges exerts impact on a gleam of vessels and, therefore, on regulation To. river.

Local mechanisms K. rubles are under the constant neurohumoral control providing optimum level of blood supply of various bodies in the conditions of their rest or at interaction of an organism with the environment (see. Neurohumoral regulation ). Regional distinctions are provided with the unequal density of an adrenergic innervation of vessels in various bodies and consistently located departments of a vascular bed. Due to distinctions in density of an innervation, quantity of neurotransmitters and intensity of an impulsation in sympathetic nerves adaptive changes of regional resistance to a blood flow are carried out. So, the high density of an innervation of blood vessels of skin provides its active participation in thermoregulatory processes. More expressed neurogenic increase in resistance in well innervated precapillary vessels of muscles in comparison with post-capillary leads to decrease in intra capillary pressure and absorption of liquid from intercellular space during the falling of arterial pressure (see. Capillary pressure ). Different sensitivity of unstriated muscles of various regional networks to vasculomotor can be one of the reasons of differentiation of vascular reactions to mediators (see) or to action of local metabolites. E.g., excitement of sympathetic fibers of skeletal muscles causes rather resistant vasoconstriction, despite the events at the same time accumulation of vasodilating metabolites. The same phenomenon in intestines leads only to temporary reduction of a blood-groove.

Some vascular zones are innervated by the vasodilating fibers which do not have tonic activity. So, e.g., at reaction of the protection caused by irritation of a hypothalamus cholinergic sympathetic fibers, the innervating vessels of resistance of skeletal muscles are activated. It leads to redistribution of a blood-groove in favor of skeletal muscles (at the same time there is an activation of vasoconstrictor nerves in other vascular areas). Parasympathetic vasodilating fibers are found in vessels of sialadens, some glands went. - kish. a path where they act, apparently, together with the bradykinin which is formed there.

A variety of regional vascular reactions in response to action of neurohumoral mediators is tried to be treated from positions of existence of specific formations of a membrane of smooth muscle cells (i.e. alpha and beta adrenoceptors, holinoretseptor, etc.) - It is considered that excitement of alpha adrenoceptors leads to vasoconstriction, and beta adrenoceptors — to their expansion. So, e.g., the increase in a blood-groove in a myocardium, skeletal muscles and a liver caused by administration of adrenaline is explained by a large number of beta receptors in these vessels or unequal affinity of beta receptors of various areas of a vascular bed to adrenaline.

The most widespread and widely studied indicator of a condition of a regional vascular bed is its resistance to a blood-groove showing with what perfused pressure through 100 g of fabric of body 1 ml of blood in 1 min. proceeds. For calculation of this size it is necessary to know rate of volume flow of a blood-groove through body and pressure in the arterial and venous ends of a vascular bed (see. Hemodynamics ). The applied methods of perfusion isolated (in the hemodynamic relation) bodies allow to avoid influence on the studied vascular bed of changes of the central arterial and venous pressure, shifts in chemical and physical. composition of blood that is especially important during the studying of active reactions of vessels and neurohumoral regulation To. river. At perfusion with strictly constant volume of blood (rezistografiya) criterion of shifts of resistance changes of perfused pressure at an entrance to an artery serve, and with the stabilized pressure — amount of the blood proceeding through body. Changes of a krovenapolneniye of body bear important information on a condition of capacity vessels. For registration of this size use methods radiotsirkulografiya (see), pletizmografiya (see) etc.

Researches of vessels in a microcirculating bed include change of size of their gleam, pressure, speed of a blood-groove, processes of diffusion, filtering and absorption, a mikropinotsitoz. On the basis of definition of exchange of water between capillaries and fabrics average pressure in a capillary bed of body and the coefficient of capillary filtering serving as an indicator of permeability of capillaries and the areas of a perfusing surface is calculated. For judgment of a condition of exchange it is important to have an idea about hydrostatic and the colloid osmotic pressure of intersticial liquid.

Age and sexual features To. rubles are connected with the level of a metabolism in fabrics, a condition of a vascular bed, its reactivity to neurogenic and humoral influences.

Practically all types of pathology to a greater or lesser extent mention cardiovascular system. At the same time it is broken also To. the river, degree of manifestation to-rogo depends on features of a structure of vascular networks of bodies and their regulation. Especially serious effects arise at disturbances of blood circulation in vitals (see. Coronary circulation , Cerebral circulation , Portal blood circulation ).

See also Blood circulation , Cardiovascular system .


Bibliography: Gabriyelyan E. S. Some aspects of physiology and pharmacology of cerebral circulation, Yerevan, 1976, bibliogr.; Kupriyanov V. V., Karaganov Ya. L. and To about z l about in V. I. Mick-rotsirkulyatornoye a bed, M., 1975, bibliogr.; Levtov V. A. Chemical regulation of local blood circulation, L., 1967, bibliogr.; Regulatory mechanisms of cells of smooth muscles and myocardium, under the editorship of R. S. Orlov, L., 1971, bibliogr.; Tkachenko B. I. and d river. Regional and system vasomotor reactions, L., 1971, bibliogr.; Chernukh A. M., Alexandrov P. N. and Alekseev of O. V. Mikrotsirkulyation, M., 1975, bibliogr.; Shushengko K. A. Circulatory capillaries, Novosibirsk, 1975, bibliogr.; The peripheral circulation, ed. by R. Zelis, N. Y., 1975.


B. I. Tkachenko.

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