A portal triad (also known as portal field, portal area, or portal tract) is a distinctive arrangement in the liver. It is a component of the hepatic lobule. It consists of the following five structures:
- proper hepatic artery, an arteriole branch of the hepatic artery that supplies oxygen
- hepatic portal vein, a venule branch of the portal vein, with blood rich in nutrients but low in oxygen
- one or two small bile ductules of cuboidal epithelium, branches of the bile conducting system.
- lymphatic vessels
- branch of the vagus nerve
The misnomer "portal triad" traditionally has included only the first three structures, and was named before lymphatic vessels were discovered in the structure. It can refer both to the largest branch of each of these vessels running inside the hepatoduodenal ligament, and to the smaller branches of these vessels inside the liver.
In the smaller portal triads, the four vessels lie in a network of connective tissue and are surrounded on all sides by hepatocytes. The ring of hepatocytes abutting the connective tissue of the triad is called the periportal limiting plate.
- Histology image: 15203loa – Histology Learning System at Boston University - "Liver, Gall Bladder, and Pancreas: liver; portal triad"