Tetrapod probably had a three-chambered heart, as do modern amphibians and reptiles, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enters by separate atria, and is directed via a spiral valve to the appropriate vessel — aorta for oxygenated blood and pulmonary vein for deoxygenated blood. The spiral valve is essential to keeping the mixing of the two types of blood to a minimum, enabling the animal to have higher metabolic rates, and be more active than otherwise. The difference in density between air and water causes smells (certain chemical compounds detectable by chemoreceptors) to
Deep vein of the thigh Deep vein of the thigh The deep vein of the thigh, (profunda femoris vein or deep femoral vein) is a large deep vein in the thigh. It receives blood from the inner thigh and proceeds superiorly and medially running alongside the profunda femoris artery to join with the femoral vein approximately at the level of the inferior-most portion of the ischial tuberosity. The deep vein of the thigh contributes the largest volume of blood to the femoral vein. The deep vein of the thigh is commonly affected by phlebitis which can be a dangerous condition in the case of a