So remember, when the placenta was actually developed, the Corian released these digestive enzymes that digested tiny holes inside these maternal blood vessels. And those holes essentially allow the blood to actually leak out. So the way that the exchange takes place is within the maternal blood. Within the pool of maternal blood we have oxygen. And oxygen moves down its concentration gradient from the pool of blood and into the capillaries of that fetus. At the same time, carbon dioxide is deposited out of the capillaries of that fetus and into the pool of blood and eventually picked up by the maternal blood veins.