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
Great arteries of the aortic arch. The 5th pair of vessels only form in some cases without any known contribution to the final structure of the great arteries. The right 6th almost completely regresses with only the proximal part contributing to the base of the pulmonary arteries, while the left 6th forms the ductus arteriosus, which disappears after birth. Abnormalities in the development of the great arteries during embryonic development may lead to congenital cardiovascular defects, such as: Some of these defects can be asymptomatic and cause no complications in patients, with others being more severe and require immediate surgery right after