Physiology of the Mesenteric Circulation

The mesenteric circulation is responsible for the blood supply to the small intestine, ascending colon and the proximal two-thirds of the transverse colon. Control of blood flow in the mesenteric circulation occurs at the level of the microcirculation consisting of microscopic arteries and arterioles, capillaries and microscopic veins. Autoregulation of blood flow within the mesentery is achieved by a variety of mechanisms. These include direct vasodilator effects on mesenteric blood vessels caused by tissue hypoxia and accumulation of metabolic byproducts. Osmotic factors are also involved with vasodilation. Myogenic pathways, cardiovascular influences, the autonomic system and neurohumoral factors all have significant roles in mesenteric blood flow. A thorough description of the influences of these and standard fluid dynamics of blood flow are included in this chapter.