BLOOD DEPOT

From Big Medical Encyclopedia

BLOOD DEPOT — the body or fabric having ability to accumulate a significant amount of blood in the vessels a cut if necessary can be used by an organism. To. serve one of effector devices funkts, the system supporting the volume of the circulating blood in an organism. Value K. consists in a possibility of bystry increase in the volume (weight) of the circulating blood necessary for ensuring requirements of an organism at present. At absence To. even minor change of capacity of vascular system would lead to falloff of inflow of blood to heart and falling of the ABP (see. Blood circulation ). Mobilization of blood from depot is caused by the emotional tension, intensive muscle performance, a condition of air hunger of an organism, blood loss, etc. Changes of level of blood supply and a krovenapolneniye take place in all bodies and body tissues since in all cases first of all blood goes to intensively working bodies. However a role To. carry out only spleen (see), liver (see), lungs (see), skin (see) as vessels of these bodies are capable to detain a large number additional, reserve, the blood used in case of emergency by other bodies and fabrics. Mechanisms of deposition of blood and its mobilization are specific to each of these bodies.

the Scheme of filling with blood and emptyings of a sine of a spleen (blood is designated in black color): 1 — a vein, 2 — an efferent sphincter, 3 — a sine of a spleen, 4 — an afferent sphincter; and — the sine «is included» in blood circulation (efferent and afferent sphincters are open); and in — gradual filling of a sine (the efferent sphincter is closed); — the sine is filled with blood and disconnected from circulation; d — the beginning of emptying (the efferent sphincter is open); shooters designated the direction of a blood flow

In to spleen the person — in its venous sine about 8 — 12% of total quantity of blood can accumulate. The delay of blood arises owing to reduction of the ring muscles located on site transition of a sine to a vein. Build-up of pressure of blood in sine and the bringing capillaries promotes transition of a blood plasma to the intercellular lymph and a lymph flowing from a spleen (fig). Thanks to it blood in sine becomes more concentrated (in experiences on J. Barkroft's dogs showed that blood in a spleen may contain up to 1/5 total quantities of erythrocytes of all blood). At sharp increase of need of an organism for oxygen there is an excitement of a sympathetic nervous system, sphincters of sine relax and their contents come to blood. Bystry emptying of a spleen is promoted also by the active reduction of unstriated muscles of the capsule of a spleen and its trabeculas arising at excitement of a sympathetic nervous system. Receipt at the same time of a large number of erythrocytes in a blood stream leads to growth of a hematocrit and increase in amount of hemoglobin of blood. It improves transport of oxygen and carbonic acid, promotes fuller satisfaction of needs of an organism for oxygen.

In hron, an experiment it was revealed that reduction of a spleen happens at emotional pressure or at the hyperphrenia previous physical. to loading. Other factors promoting release of blood from a spleen are bleeding, introduction to an organism of drugs, etc.

Liver it is also capable to deposit and concentrate significant amounts of blood, however, unlike a spleen, the liver serves not only To., but also, being located on an outflow tract of blood from a portal bed, forms the peculiar lock of all portal system regulating its filling or emptying. In a liver there is no full switching off of blood from the general blood-groove. The ground mass of blood is concluded in the sinusoids forming the anastomosing vascular network and in vessels of venous system. Deposition of blood in a liver can result or reductions of a diffusion sphincter of hepatic veins and sinusoid at invariable inflow of blood, or due to the increased inflow of blood at its invariable outflow. Relaxation of an output sphincter promotes mobilization of depot. From hepatic depot influences a bystry exit of blood adrenaline (see) which causes sharp narrowing of mesenteric arteries and consequently, reduction of inflow of blood to a liver, simultaneous expansion of output sphincters and reduction of sinusoid (see. Portal blood circulation ). It leads to bystry emptying of hepatic depot and reduction of a liver in sizes. Outflow of blood from a liver depends on fluctuations of pressure in system of the lower vena cava and in an abdominal cavity. Increase in cordial emission and intensity of respiratory movements, and also reduction of muscles of a prelum abdominale promote mobilization of the blood deposited in a liver and strengthening of its inflow to heart.

Lungs play a role To. due to change of capacity of their venous and arterial systems. Blood in arteries of lungs is under the pressure of 5 — 6 times lower, than in arteries of a big circle of blood circulation. Besides arteries of lungs have rather thin and more extensible walls and to a large extent, than arteries of a big circle, can change the volume. Reduction of muscles of arterioles and precapillaries promotes a delay of considerable mass of blood in arterial system of a small circle. The main tanks of blood in lungs are the pulmonary veins containing more than a half of volume of the blood circulating on a small circle. Easily extensible walls of pulmonary veins allow them to contain additional amount of blood, edges can be deposited in this site of a vascular bed or be mobilized from it at change of inflow of blood to the right heart and lungs or change of force of reductions of a left ventricle.

It is established that after removal of a cuff or plaits from the hips causing stagnation of blood in legs about 600 ml of blood can quickly come to a blood channel. However sharp increase in minute volume of a left heart at the same time does not happen since nearly 80% of this blood are deposited in vessels of lungs.

Deposition of blood increases in lungs at influence of the factors causing vasoconstriction of a big circle of blood circulation. Thus, between volumes of blood in vessels of small and big circles of blood circulation reciprocal relationship is observed. Deposition of blood sharply increases in lungs at insufficiency of sokratitelny function of a left heart. This reaction facilitates function of heart and at the same time leads to reduction of vital capacity of lungs that can lead to development in certain cases respiratory insufficiency (see).

Skin — very peculiar To. The main function of skin — protective. Besides, change of a tone of vessels of skin plays an important role in thermal controls (see). At the same time venules and veins of a subpapillary layer of skin can contain large additional number (to 1 l) blood. Normal at healthy people the depositing function of vessels of skin is expressed not so clearly, as at the listed above bodies because change of a gleam of vessels and blood supply of skin first of all are connected with processes of thermal control.

The volume of the deposited blood in an organism is very various and depending on needs can increase or decrease. Process of emission of blood of depot, as well as its filling, is under the regulating influence of c. N of page. An example of neurogenic change of volume To. can serve the reflex shifts in the blood circulatory system in response to build-up of pressure in a small circle of blood circulation described in 1939 by V. Larin. To them it was established that build-up of pressure in vessels of lungs leads to expansion and increase in a krovenapolneniye of the main depot — spleens with simultaneous bradycardia and decrease in the ABP (a so-called reflex of Larin).

Function of deposition of blood can be investigated straight lines and indirect methods. So, about the size of deposition of blood in a liver or in a spleen judge by simultaneous measurement of rate of volume flow of inflow and outflow of blood from these bodies. It is also necessary to carry to number of direct ways and rentgenol, Barkroft's method (1925). By this method at the edges of a spleen place metal clips and remove the roentgenogram in two perpendicular directions. Then according to a X-ray analysis build the surface area of a spleen, on a cut define change of its krovenapolneniye. In the indirect way the volume of the deposited blood can be determined on change of the volume (weight) of the circulating blood, napr, before and after physical. loadings.

See also Deposition .



Bibliography: Barkroft. The main lines of architecture of physiological functions, the lane with English, M. — L., 1937; Botkin S. P. Course of clinic of internal diseases and clinical lectures, t. 1 — 2, M., 1950; Larin V. V. and Meerson F. 3. Sketches of clinical physiology of blood circulation, M., 1965; Folkov B. and Neil E. Blood circulation, the lane with English, M., 1976; WrightS. Applied physiology, L. and. lake, 1961.

G. I. Kositsky, I. N. Dyakonova.

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