And these are the cells that are responsible for contracting and creating that hydrostatic pressure that is needed to pump all that blood through all the blood vessels of our body. Now, the innermost portion of the heart that is in direct contact with the blood of our chambers, found inside the chambers of the heart, this is known as the endocardium. And the endocardium consists of endothelial cells of simple squamous opel cells that are in direct contact with the blood found inside our chambers. So once again, the heart can be broken down into three layers. So we have our epicardium, we have the myocardium and we have the endocardium. And these three layers form four different chambers inside our heart.