From Big Medical Encyclopedia

STAZ (Greek stasis standing) — a local stop in a gleam of this or that body of its physiological contents.

Distinguish a hemostasis (S. of blood, or blood S.), duodenostaz (a long delay of a chyme in a duodenum), a cholestasia (stagnation of bile in bilious channels), a lymphostasis (the termination limfoto), a coprostasis (stagnation a calla in a large intestine). However understand a local stop of a blood-groove in a microcirculator bed as S., hl more often. obr. in capillaries and adjacent the smallest to them arteries and veins.

S.'s studying blood in capillaries in essence began with researches of microcirculation in transparent areas of bodies of animals (see. Mikrotsirkulyation ). To the middle of 20 century staz blood were explained differently, napr, with haemo concentration in capillaries owing to increase in permeability of their walls for a blood plasma, tackifying of erythrocytes, etc. Convincing experimental proofs of origins of S. began to appear only in the second half of 20 century.

In the equation of a hemodynamics of Q=ΔP/R where Q — the size of a blood-groove in vessels, ΔP — a pressure gradient on their extent, a R — resistance to a blood-groove in them, determine the size of a blood-groove in separate vessels and bodies by Krom, major factors are reflected, from to-rykh delay and a stop of a blood-groove at S. depends (see. Hemodynamics ). Follows from the equation that S. can be caused by reduction of swing pressure throughout a microvessel and (or) increase in resistance in its gleam.

Depending on the reasons which caused S. distinguish ischemic (see. Ischemia ), congestive and true capillary Page. At ischemic S. the pressure gradient in microvessels decreases owing to considerable pressure decline in their arterial departments that can be connected with the termination of inflow of blood from larger arteries, napr, because of fibrinferment (see), embolisms (see), a spasm (see. Vasomotor spasm ), etc. Congestive S. arises at reduction of a pressure gradient throughout microvessels owing to sharp build-up of pressure in their venous departments at stagnation of blood owing to venous hyperemia (see), fibrinferment of larger veins, prelums their tumor, etc. True capillary S. is connected with significant primary increase in resistance to a blood-groove in the corresponding microvessels. Such S. can be created in an experiment provided that the pressure gradient throughout capillaries remains invariable. To examination patofiziol. true capillary S.'s mechanism the experiments which established what the reason of delay and a stop of a blood-groove in capillaries is strengthened intravascular promoted aggregation of erythrocytes (see). Aggregation of erythrocytes of in vitro was in details studied by A. L. Chizhevsky, and in vivo — Naysli (M. H. Knisely) with sotr., to-rye described the strengthened aggregation of erythrocytes in microvessels of a conjunctiva of an eye of the person at pathology. Researchers considered that this phenomenon arises systemically (in all volume of blood) and causes obstruction of the smallest arterioles, i.e. breaks microcirculation. The role of local aggregation of erythrocytes as S.'s reasons for the first time was shown by G. I. Mchedlishvili. Further by many researchers it was shown that ability of erythrocytes to form units in vessels is the major factor defining a viscosity grade and consequently, and flowabilities of blood (rheological properties) in microvessels.

True capillary S.'s development is promoted by primary delay of speed of a blood-groove in capillaries (e.g., at venous stagnation, an inflammation, ischemia) when flow pattern of blood in microvessels changes in such a way that facilitates aggregation of erythrocytes. S.'s emergence is also promoted by rather high concentration of erythrocytes in the blood flowing on capillaries (e.g., at giperemiya), at the same time colliding of erythrocytes among themselves and their aggregation is facilitated. The page develops more often in venous departments of capillaries where permeability of walls is higher. When pathogenic factors promote sharp increase in permeability of walls of capillaries, especially in their venous departments, water and finely divided albumine quickly gets into fabrics from blood: increase in content in blood of globulinovy and fibri-nogenovy fractions of plasma proteins leads to the strengthened aggregation of erythrocytes and Page.

Development and true capillary S.'s permission are influenced by nervous and humoral mechanisms. The nervous system influences intravascular aggregation of erythrocytes by means of physiologically active agents playing a role of transmitters of nervous impulses. So, at action of acetylcholine (rather high concentration) in capillaries there is S., the histamine works opposite. Nervous influences on development and true capillary S.'s permission can be carried out also by means of change of conditions, from to-rykh its development depends. So, the konstriktion of the bringing arterioles caused by neurohumoral influences and the delay of a blood-groove caused by it in capillaries promotes S.'s development, and the neurogenic dilatation of arterioles causing acceleration of a blood-groove, on the contrary interferes with intra capillary aggregation of erythrocytes and provides permission of Page.

Circulatory capillaries at S. on gistol. drugs look expanded and filled with homogeneous contents, in Krom of border of erythrocytes are indiscernible in this connection it has an appearance of homogeneous gialinopodobny mass. However at electronic microscopic examination in these cases accurate contours of erythrocytes, skintight to each other are defined. At a long staz there is a disintegration of thrombocytes to the subsequent loss of fibrin and formation of blood clot (see. Thrombosis ).

As the stop of a blood-groove in capillaries at S. causes the termination of delivery of oxygen (see. Hypoxia ) and nutrients to the respective sites of fabric, manifestation of a staz are similar to symptomatology ischemia (see). The outcome of a staz depends on its duration and the place of emergence. Short-term staz — the phenomenon reversible. Rather skoroprokhodyashchy S., especially in fabrics, insensitive to disturbances of blood supply (e.g., connecting fabric and its derivatives), can not be followed by any effects. If S. remains for a long time, covers a large number of capillaries and occurs in fabrics, highly sensitive to disturbances of blood circulation, in hard cases there can come the necrosis of separate structural elements or fabric (see. Heart attack , Necrosis ). First of all it belongs to c. N of page, especially sensitive to any disturbances of blood supply.

Bibliography: Small L. T., Miklyaev I. Yu. and To r and in the h at P. G. Mikrotsirkulyation's N in cardiology, Kharkiv, 1977; Mchedlishvili G. I. Microcirculation, Tbilisi, 1958; Chernukh A. M., Alexandrov P. N. and Alekseev of O. V. Mikrotsirkulyation, M., 1975; Chizhevsky A. JI. Structural analysis of moving blood, M., 1959; Handbook of physiology, Sect. 2 — Circulation, ed. by W. F. Hamilton, v. 3, Washington, 1965.

G. I. Mchedlishvili.