So this is the left atrium. The left atrium, once it fills with blood, it moves into the left ventricle. And it's the left ventricle that is the thickest of all these chambers. It contains the thickest layer of myocardium and that means it can create the highest hydrostatic pressure. And that is important because it's this ventricle that is responsible for moving all that blood into the order and all the different organs and tissues and cells of our body. So we have the right atrium, the right ventricle that make up the right pump of the heart.