Anatomy, Abdomen and Pelvis, Portal Venous System (Hepatic Portal System)

The veins that drain the gastrointestinal organs parallel the major arteries that supply the foregut, midgut, and hindgut, including the celiac, superior mesenteric, and the inferior mesenteric arteries respectively. These veins eventually convene at the portal vein, forming a single venous inflow tract into the liver. The celiac vein drains the foregut structures, including the stomach, through the second part of the duodenum. The superior mesenteric vein drains the third part of the duodenum through the initial two-thirds of the transverse colon. Finally, the inferior mesenteric vein drains the remaining one-third of the transverse colon through the rectum. These veins comprehensively drain nutrients and toxins from the digestive intake and ultimately provide approximately 75% of the liver's blood supply, the remainder coming from the hepatic artery, eventually draining into the hepatic veins and systemic circulation.