Now, if the pressure is higher on the right atrium than on the left atrium, as it is in the case of that fetus, the pressure will create a force that will push on the septum. Premium will push on this door and will open the door, allow the movement of blood from the right atrium to the left atrium. So remember, inside the fetus, the reason we have a higher pressure in the right side of the heart in the right atrium than the left side of the heart, the left atrium, is because of the lungs. The lungs have a high resistance, create a high pressure to flow, and that causes a high pressure to exist in the pulmonary trunk as well as the right ventricle and the right atrium. And so that's exactly why the blood will be shunted away from the lungs, will bypass the lungs and go directly from the right atrium into the left atrium, then into the left ventricle, and then into the order. Now, of course, some amount of that blood will still leak into the right ventricle from the right atrium.