And we have the left atrium and the left ventricle that make up the left pump of our heart. And these pumps work at the same exact time. And that means when the right pump contracts, the left pump contracts at the same time. And when the right pump relaxes, our left pump relaxes at the same exact time. So when the right ventricle contracts, the left ventricle contracts at the same time. Now, we know that inside our cardiovascular system the blood actually flows in only one direction.