Which veins unite to form the portal vein?

• A. Splenic and Superior Mesenteric
• B. Inferior Mesenteric and Splenic
• C. Left Gastric and Splenic
• D. Superior Mesenteric and Left Gastric

Answer: (A)

Blood from the gut reaches the liver through the hepatic portal vein, which is formed by the union of the splenic vein and the superior mesenteric vein behind the neck of the pancreas. The splenic vein drains spleen and stomach/pancreatic veins, while the superior mesenteric vein collects blood from the small intestine, most of the large intestine, and the pancreas. When these two vessels join, they create the portal vein that then enters the liver and divides into left and right branches.

Other veins participate in the portal system but do not form the main trunk. The inferior mesenteric vein typically drains into the splenic vein (or less commonly into the superior mesenteric vein) rather than forming the portal vein itself. The left gastric vein and other tributaries drain into the portal vein, but they do not create the portal trunk.