We have the right lung and we have the left lung. Now, within the lung, we have an exchange taking place. We basically bring oxygen into the blood and we expel our carbon dioxide from our blood into the outside environment. So when we inhale, we bring in that oxygen into our blood. And when we exhale, we basically remove that carbon dioxide from our system, from our blood. Now, in number five, once we actually oxygenate this blood within the lungs, we then take that oxygen blood and we move it through the venuels and through our pulmonary vein.