Hepatic Circulation - refers to liver blood flow. Mesenteric Circulation - refers to intestinal blood flow. Blood collected from all of the alimentary organs flows into the portal vein. The positioning of the liver at the entrance for blood into the systemic circulation is critically important for screening substances absorbed from the alimentary canal. Flow along the length of the intestinal tract is regulated by tissue activity providing local control.
Blood flow is distributed differently to specific layers of the intestinal wall.
The highest flow is found in the submucosa followed by the mucosa and then muscle layers. This allows elevated blood flow to local regions where activity is high. Therefore, general sympathetic outflow elicits significant redistribution of blood out of the splanchnic circulation. Eventually buildup of local metabolites near areas of active absorption will autoregulate flow to that specific area of the tract. This points to the local vs. general regulation of all processes associated with digestion-absorption.