Circulatory system the areas above the heart) and the inferior vena cava (roughly speaking from areas below the heart). These two great vessels empty into the right atrium of the heart. The heart itself is supplied with oxygen and nutrients through a small "loop" of the systemic circulation and derives very little from the blood contained within the four chambers. The general rule is that arteries from the heart branch out into capillaries, which collect into veins leading back to the heart. Portal veins are a slight exception to this. In humans the only significant example is the hepatic portal vein which
Circulatory anastomosis Circulatory anastomosis A circulatory anastomosis is a connection (an anastomosis) between two blood vessels, such as between arteries (arterio-arterial anastomosis), between veins (veno-venous anastomosis) or between an artery and a vein (arterio-venous anastomosis). Anastomoses between arteries and between veins result in a multitude of arteries and veins, respectively, serving the same volume of tissue. Such anastomoses occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised, but may also occur pathologically. Arterio-arterial anastomoses include actual (e.g., palmar and plantar arches) and potential varieties (e.g., coronary