41. Splanchnic circulation

The splanchnic organs include the stomach, small intestine, large intestine, pancreas, spleen, kidney and liver. The splanchnic circulation refers to all blood flow which originates from the celiac trunk, superior mesenteric artery and inferior mesenteric artery.

The splanchnic organs receive a lot of blood flow in rest, as it is during rest that the gastrointestinal tract and kidneys works the most and therefore requires the most blood. In rest around 20% of the blood is in the splanchnic circulation.

Regulation of the splanchnic circulation:

However, during exercise the gastrointestinal tract doesn’t work that much and therefore requires much less blood. During exercise, the splanchnic blood flow is reduced and the extra blood is instead redirected to other organs like the skeletal muscles, heart and lungs.

The splanchnic circulation is heavily innervated by sympathetic and parasympathetic nerves. During exercise the sympathetic nervous system is activated. This causes arterioles in the splanchnic circulation to vasoconstrict, which reduces the blood flow to it. During rest the parasympathetic nervous system is activated, which vasodilates the arterioles.