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 and nutcracker syndrome (renal vein entrapment syndrome). Renal vein The renal veins are veins that drain the kidney. They connect the kidney to the inferior vena cava. They carry the blood filtered by the kidney. There is one vein per kidney, that divides into 4 divisions upon entering the kidney: Because the inferior vena cava is on the right half of the body, the left renal vein is generally the longer of the two. Because the inferior vena cava is not laterally symmetrical, the left renal vein often receives the following veins: This is in contrast to the right side