The portal circulation

The portal circulation (synonym portal circulation - the system of blood supply to the abdominal organs receiving the arterial blood from the celiac and mesenteric arteries.
From celiac, mesenteric and splenic artery blood pressure 110 to 120 mm RT. senior enters the so-called first network of capillaries portal bed, located in the intestine, stomach, pancreas and spleen. From there, under the pressure of 15-20 mm RT. Art. it is sent to the venules, Vienna and later in the portal vein (see), where the pressure is 10-15 mm RT. Art. From the portal vein blood enters the so-called second network of capillaries portal bed, located in the liver, i.e. in the hepatic sinusoids, pressure ranges within 6 - 12 mm RT. Art. Out the blood system of the hepatic veins enters into the inferior Vena cava, leaving a portal channel (printing. table).

the scheme portal circulation
The scheme portal circulation: 1 - v. lienalis; 2 - v. mesenterica Inf.; 3 - v. mesenterica sup.; 4 - v. portae; 5 - branching of blood vessels in the liver; 6 - vv. hepaticae; 7 - v. cava inf.

One of the branches of the celiac artery - hepatic artery - goes to the liver (see), where blood capillary flow directly into the liver venules and sine waves, i.e. the second capillary network. The blood flowing through the arteries, is intended to supply the liver oxygen and consequently passes first capillary network. The pressure difference in the initial and final parts of the portal bed, component 100-110 mm RT. century, provides a steady flow of blood. In humans through the portal part is on average 1.5 liters of blood in 1 min. Time of blood flow from the beginning of the mesenteric arteries through both capillary network to hepatic veins - 20 sec.; from the beginning of the hepatic artery through the vessels of the liver and the hepatic veins - 11 sec.
Portal channel is the main depot of blood in the body. In the exercise of the functions of the Deposit play an important role diffuse vascular sphincter, located in the liver and regulate the outflow of blood from the portal bed, and muscles mesenteric artery tone which regulates the amount of blood flow in the portal direction.
The ratio of vascular tone, which occur outflow and inflow of blood, determines the number in the portal vein. OK, this value is about 20% of the total volume of blood contained in the body, but in certain pathological conditions may increase to 60% and more.
Important Department of a portal channel - the circulation of the blood in the liver, but to which the portal vein flow about 80% of the blood g by hepatic artery - 20% . Features of blood flow in the liver closely related to the structure of intrahepatic vessels. So, in liver tissue there is a wide arteriovenous anastomoses between the branches of the portal vein and hepatic artery. The value of this anastomosis in the norm is that to liver cells do not clean the portal or arterial blood, and the mixture portal and arterial blood, optimum for the implementation of hepatic cells is their metabolic functions. If bandaging the hepatic artery, the liver will be supplied with blood, flowing only in the portal vein. If you create Porto cavalry anastomosis Ecka (fistula Ekka), giving thus the portal circulation, bypassing the liver, the liver will be fully supplied arterial blood. Any pronounced violations of metabolic and excretory functions of liver neither is any other case, is not observed. Therefore, in the liver, there is vzaimozavisimost portal and arterial blood flow. Based on this surgery used in the treatment of portal hypertension.
Small intrahepatic vessels - terminal venules portal system, sine wave, Central vein, hepatic artery branching have high vasomotor activity. Adrenaline causes spasm of sinusoidal, disclosure output sphincters and throwing away the blood from the liver in the General direction of circulation. The introduction of a hypertonic NaCl or 40% glucose solution causes spasm intrahepatic vessels, and after 20 minutes - their expansion. Cold stimulation of skin receptors, injury distant organs and tissues, blood loss leading to spasm intrahepatic vessels; the application to the skin heat is to their expansion. The third part of the inner surface of sinusoidal liver covered the so-called mapfromscene cells that, as part of the reticuloendothelial system (see), phagocytic bacteria and fixed in their cytoplasm foreign substances.
Nervous regulation of portal blood circulation is vegetative centers under certain degree of cortical control. In all departments portal channel there are numerous baroretseptorov, irritation which tensile portal vessels of high pressure leads to increase in blood pressure in the pulmonary circulation. The sympathetic innervation portal channel originates from neurons of the side columns III - XI thoracic segments of the spinal cord. Upon excitation of the sympathetic centres there is a sharp narrowing of the branches of the portal vein and sinusoidal liver; increases portal pressure. Excitation system of the vagus nerve leads to the opposite result.