Blood flow in the liver

Through the liver every minute, 1,500 ml of blood flows, with 2/3 of the volume of blood flowing through the portal vein and 1/3 - through the hepatic artery.

In the arterial bed of the liver, blood comes from the common hepatic artery (a hepatica communis), which is the branch of the trunk cortex (truncus coeliacus). The length of the common hepatic artery is 3-4 cm, diameter 0.5-0.8 cm.

The hepatic artery directly above the doorkeeper, not reaching 1-2 cm to the common bile duct, is divided into gastroduodenal (a gastroduodenalis) and its own hepatic (a.hepatica propria) artery.

Its own hepatic artery passes in the hepatic-duodenal ligament, its length varies from 0.5 to 3 cm, diameter from 0.3 to 0.6 cm. Further, the hepatic artery is divided into the right and left branches (this occurs directly in the gates of the liver or before entering into them). The left hepatic artery supplies the left, square and caudal lobes of the liver. The right hepatic artery blood supply basically the right share of the liver and gives the artery to the gallbladder.

Inside the liver, the branches of the hepatic artery dichotomously divide and in the terminal portal tracts they are terminal branches (arterioles). The diameter of the arteriol is 10-15 μm, its wall contains elastic fibers, sometimes - smooth muscle fibers in the form of bundles. Thus, arterioles can form precapillary sphincters. On the periphery of the portal field, the hepatic arterioles perforate the border plate and flow directly into the sinusoids. The walls of the sinusoids are lined with endothelium. Sinusoids are located between the beams (trabeculae) of hepatocytes. The branches of the hepatic artery give their blood to sinusoids both on the periphery and in the center of the lobules.

The venous system of the liver is represented by the leading and draining veins. The main leading vein is the portal one. The outflow of blood from the liver occurs through the hepatic veins, which flow into the lower vena cava.

The portal vein (v. Portae) begins at level II of the lumbar vertebra behind the head of the pancreas. It includes two large trunks: v. lienalis and v. Mesenterica superior, its largest tributaries are v. corvnaria ventriculi and v. Mesenterica inferior. The length of the portal vein is 6-8 cm, diameter up to 1.2 cm; it does not have valves, it collects blood from the unpaired organs of the abdominal cavity. At the level of the gates of the liver, the portal vein divides into the right branch, which supplies the right lobe of the liver, and the left branch supplying the left, tail and quadrant lobe of the liver.

Inside the liver, the branches of the portal vein run parallel to the branches of the hepatic artery, supplying blood to all the lobes and segments of the liver, disintegrating to the portal venules.

The portal venule has a diameter of 20-50 microns, its walls are formed by the endothelium, basal membrane and adventitious connective tissue, there are no smooth muscle bundles.

The terminal venule perforates the parenchymal border plate and runs into the hepatic sinusoids, which thus contain mixed arterial venous blood.

A diverting venous duct collects venous blood from sinusoids into the central (terminal) hepatic veins, the wall of which consists of the endothelium, reticulin fibers and a small amount of collagen fibers.

From the terminal hepatic venules blood enters the sublobular and collective veins, then into the right median and left hepatic veins that flow into the lower hollow vein below where it passes through the opening in the tendon part of the diaphragm into the thoracic cavity.

At the point of confluence in the inferior vena cava, the hepatic veins are blocked by the annular muscle.

The portal vein is connected by numerous anastomoses with hollow veins (porto-caval anastomoses). These are anastomoses with veins of the esophagus and stomach, rectum, peri-ocular veins and veins of the anterior abdominal wall.

Gate hemodynamics is characterized by a gradual shift from high pressure in the mesenteric arteries to the lowest pressure in the hepatic veins.

The blood pressure in the mesenteric arteries is 120 mmHg. Then the blood enters the intestinal, stomach, pancreatic capillary network, the pressure in this network is 10-15 mm Hg. From this network, blood enters the veins and veins that form the portal vein, where the pressure is normally 5-10 mm Hg. From the portal vein, blood enters the mevdolkovye capillaries, from where it enters the system of hepatic veins and passes into the lower vena cava. The pressure in the hepatic veins ranges from 5 mm Hg. To zero.

Normally, the pressure in the portal vein is 5-10 mm Hg. Or 70-140 mm.vod.st.

According to classical ideas, the functional-morphological unit of the liver is the hepatic lobule. The number of hepatic lobes is 500,000. The length of the lobule is 0.5-2 mm.

The center of the hexagonal hepatic lobe is the hepatic (central) vein, and on the periphery there is a portal field. The parenchyma of the lobes is formed by radially arranged beams (trabeculae) of hepatocytes, converging to the central (hepatic) vein. Between the beams there are sinusoids, through which the mixed arterio-venous blood flowing from the portal vein and the hepatic artery flows.

At the point of departure of the sinusoid from the terminal branch of the portal vein and at its entry into the central vein, there are smooth-muscle sphincters regulating the flow of blood into the hepatic lobe.

Sinusoids are an intraorganic (intrahepatic) capillary network. Sinusoids are modified blood capillaries, unusually wide (diameter 7-21 microns), lined with endothelium.

[1], [2], [3], [4]