The portal vein or hepatic portal vein (Latin: vena portae hepatis) is located in the upper right quadrant of the abdomen. It is typically 8 centimeters long in adults. The portal vein is responsible for carrying blood from the GI tract, gallbladder, pancreas, and spleen to the liver.
The hepatic portal vein originates behind the neck of the pancreas and is usually formed by the convergence of the superior mesenteric vein and the splenic vein, referred to as the splenic-mesenteric confluence.
Sometimes the hepatic portal vein also directly joins with the inferior mesenteric vein. It may also anastomose with the cystic and gastric veins.
The hepatic portal vein provides around 70% of blood supply to the liver (the hepatic arteries provide the rest). It enters the liver via the porta hepatis, which also serves as the entry point for the proper hepatic artery, and the point of exit for the bile passages.
Before reaching the liver, the hepatic portal vein divides into the right and left hepatic portal veins, with each side further splitting into venous branches and into portal venules, which travel along hepatic arterioles within the connective tissue between the liver lobules. Together with a common bile duct, the portal venule and hepatic arteriole create the hepatic portal triad. These blood vessels eventually empty into hepatic sinusoids to supply blood to the liver.
After the blood is processed by the main functional liver cells (hepatocytes), the blood is collected by the central vein at the core of each lobule. The blood from these central veins is ultimately collected by short right and left hepatic veins, which exit the superior surface of the liver.
The hepatic veins empty into the inferior vena cava, just before the inferior vena cava penetrates the diaphragm and enters the right atrium of the heart.