While the red blood vessel is our blood vessel called the pulmonary vein. That brings oxygenated blood from each individual alveolis and to the heart of our body, specifically to the left atrium of our body. So remember, the pulmonary artery carries the oxygenated blood away from the heart and to the lungs while the pulmonary vein carries oxygenated blood away from the lungs and to our heart. So we see that this entire section, number six is the alveolar sac that contains many of these specialized balloons shaped structures we call alveoli. And within these alveoli is where gas exchange actually takes place. So we exchange oxygen for carbon dioxide.