Now, this portion is known as a septum secumom. This portion is known as the septum premium. And this entire valve structure, door like structure that can open one way and close the other way is known as the foramen O valley. 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.