There are three sets of vascular systems that supply and return blood to the normal liver. The oxygen supply to the liver is mainly supplied by the hepatic innominate artery, which is divided into the left hepatic artery and the right hepatic artery and enters into the liver to supply the oxygen needed by the liver cells to synthesize other substances. The portal vein system is formed by the confluence of the superior mesenteric vein and the splenic vein, which supplies most of the nutrients needed by the liver. The hepatic veins are divided into the left, middle, and right hepatic veins, which converge into the inferior vena cava for further blood return. Oxygen is usually supplied through the arteries and the portal vein. After the supply of nutrients, the blood is detoxified and circulated in the liver, and then injected into the inferior vena cava for further blood circulation.