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
Femoral vein has led some physicians to falsely conclude it is a superficial vein, which has resulted in patients (with deep vein thrombosis) being denied efficacious anticoagulant or thrombolytic therapy. Femoral vein In the human body, the femoral vein is a blood vessel that accompanies the femoral artery in the femoral sheath. It begins at the adductor canal (also known as "Hunter's canal") and is a continuation of the popliteal vein. It ends at the inferior margin of the inguinal ligament, where it becomes the external iliac vein. The femoral vein bears valves which are mostly bicuspid and whose number is variable