Superior means above, while the inferior vena cava, where inferior means below, basically is our single blood vessel that carries our deoxy in blood from the organs in the lower portion of our body and to number one. So notice that number one is simply our right atrium. It's where we began. So notice that we began at zero one and we ended at zero one. And so this basically shows that the cardiovascular system is in fact a closed circuit. We have a closed cardiovascular system.