Draw at low or medium magnification a part of the pancreas in which you see an island of Langerhans. The portal vein, hepatic artery and bile duct enter the liver through the porta hepatis. These three vessels travel together through the liver parenchyma. If one of these vessels gives off a branch it is usually accompanied by branches of the other two vessels. Terminal branches of one of the vessels will consequently be accompanied by terminal branches of the other two vessels.
Portal triads are a key feature of the organization of the liver.
Portal triads are embedded in interlobular connective tissue. In its corners we find the portal triads. In cross sections, the lobule is filled by cords of hepatic parenchymal cells, hepatocytes , which radiate from the central vein and are separated by vascular sinusoids . There are other ways of dividing the parenchyma of the liver into units. Two common ways are divisions into portal lobules and liver acini.