And that's because inside the right atrium, we have a higher pressure than inside the left atrium. And so, because there is a higher pressure inside the right atrium, then inside the left atrium, blood will naturally and spontaneously move from the right atrium into the left atrium. And this is the shunting of blood that takes place between the two atrium of the fetal heart. Now, a small portion of the blood will still leak into the right ventricle and then will pass into the pulmonary trunk. So this is the pulmonary trunk that connects to the right and the left pulmonary arteries. Now, those pulmonary arteries at the pulmonaire trunk we have yet another connection between the pulmonary trunk and our aorter.