The splanchnic circulation

The splanchnic circulation is composed of blood vessels serving the stomach, spleen, pancreas, small intestine, colon and liver. The urogenital organs, including the kidneys, are not part of the splanchnic system. The three major arteries serving the splanchnic organs are the celiac, superior mesenteric, and inferior mesenteric. These parallel circuits branch into numerous smaller arteries that in some instances may form anastomoses. Blood flow to the liver occurs through two distinct routes. Approximately one-third enters via the hepatic artery (a branch of the celiac artery); another two-thirds arrives via the portal vein. The portal vein is formed by the confluence of smaller veins draining the spleen, pancreas, small intestine, and colon. All venous blood leaving the splanchnic region passes through the three major hepatic veins.