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The portal vein is not a true vein, because it conducts blood to capillary beds in the liver and not directly to the heart. It is a major component of the hepatic portal system , one of three portal venous systems in the human body; the others being the hypophyseal and renal portal systems.
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.
Portal hypertension is a condition in which the blood pressure of the portal venous system is too high. It is often the result of cirrhosis of the liver. Liver cirrhosis can lead to increased intrahepatic vascular resistance and vasodilation of portal system arteries, both of which increase pressure in the portal vein. [4]
The Couinaud classification of liver anatomy then further divides the liver into eight functionally independent segments. Each segment has its own vascular inflow, outflow and biliary drainage. [2] In the centre of each segment there is a branch of the portal vein, hepatic artery and bile duct.
In histology (microscopic anatomy), the lobules of liver, or hepatic lobules, are small divisions of the liver defined at the microscopic scale. The hepatic lobule is a building block of the liver tissue, consisting of a portal triad, hepatocytes arranged in linear cords between a capillary network, and a central vein.
hepatic portal vein (entering) The hepatic duct lies in front and to the right, the hepatic artery to the left, and the portal vein behind and between the duct and artery. It also transmits nerves and lymphatics. Sympathetic nerves - these provide afferent pain impulses from the liver and gall bladder to the brain.
In human anatomy, the superior mesenteric vein (SMV) is a blood vessel that drains blood from the small intestine (jejunum and ileum).Behind the neck of the pancreas, the superior mesenteric vein combines with the splenic vein to form the portal vein that carries blood to the liver.
A portacaval anastomosis or portocaval anastomosis is a specific type of circulatory anastomosis that occurs between the veins of the portal circulation and the vena cava, thus forming one of the principal types of portasystemic anastomosis or portosystemic anastomosis, as it connects the portal circulation to the systemic circulation, providing an alternative pathway for the blood.