The two semilunar valves, the pulmonary and aortic valves, are closed, preventing backflow of blood into the right and left ventricles from the pulmonary trunk on the right and the aorta on the left.
At this point in time, we have yet to reach the carrying capacity for humans. So yes there is a carrying capacity for humans we just haven't reach it yet.
Answer:
i dont know if its correct cause that information came from Wikipedia..