And that decreases the pressure on the right side of the heart. Now, as we have more blood being pumped into the lungs, more blood is coming out of the lungs and moving into the left side of the heart. And so eventually what happens is the pressure on the left side of the heart increases. So eventually the pressure on the right side will decrease, the pressure on the left side will increase and the pressure on the left side will become greater than the pressure on the right side of the heart. And when that takes place, that's when the foramino valley closes. So remember the septum prima, this wall will only open this way when the pressure inside the right atrium is higher than the pressure inside the left atrium.