Blood vessel prevent backflow as a result of a decrease in blood pressure as the blood passes through the circulatory system. There are various kinds of blood vessels: They are roughly grouped as "arterial" and "venous", determined by whether the blood in it is flowing "away from" (arterial) or "toward" (venous) the heart. The term "arterial blood" is nevertheless used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen. This is because they are carrying the blood to and from the lungs, respectively, to be oxygenated. Blood
Renal vein directly into the IVC. Often, each renal vein will have a branch that receives blood from the ureter. It is usually singular to each kidney, except in the condition "multiple renal veins". In some people the left renal vein passes behind the abdominal aorta instead of in front of it, this is termed a retroaortic left renal vein, which is also known as "The Vein of Schnitker." If there is both a vein passing in front of and one behind the aorta this is called a circumaortic renal vein. Diseases associated with the renal vein include renal vein thrombosis (RVT)