So our blood, that is deoxygenated returns from the upper portion of the body via the superior vena cava. And the de oxygenated blood comes from the lower portion of the body via the inferior vena cava. And these two blood systems basically connect and they empty out into the right atrium of our heart, which is this chamber here. So the right atrium begins to fill with deoxygenated blood and at this moment in time, it is fully relaxed. Now, at the same exact moment in time, the oxygenated blood that is coming back from the left lung found in this section and the right lung, found in this section that blood is coming back via the right and the left pulmonary vein. So we have the right pulmonary vein which is shown in the back of this diagram, and this is the left pulmonary vein.