Large respiratory surface areas help an organism to have a more efficient gas exchange. The respiratory surface consists of an alveolar epithelial cell and a pulmonary capillary endothelial cell and it enables the movement of O2 and CO2 through it. The movement goes from the alveolar air into the blood for the O2, while CO2 moves in the opposite direction. With larger surface area more erythrocytes can pass and the more O2 can be received.
