The portal triad is a triangular or round area between three adjacent lobules. It consists of fibroconnective tissue, and contains interlobular veins, interlobular arteries, interlobular bile duct, and lymphatic vessels.

The interlobular veins, preterminal branches of the portal vein, transport nutrients and some poisonous substances from the intestine to the liver, where the hepatocytes absorb, process, and detoxify them. The arterial blood carried by the interlobular arteries, preterminal branches of hepatic arteries, is rich in oxygen. It is utilized by the hepatocytes for metabolism. The blood from both portal vein and hepatic artery mixes after entering the lobule. It flows between the hepatic plates in the sinusoid to the central vein. The blood from the central vein is collected by the sublobular vein, then passes via the hepatic vein to the inferior vena cava. The sublobular vein drains two or three central veins, running without any accompanying vessel. It has a larger lumen than the central vein, and its endothelium is enclosed by a layer of connective tissue.