So we have a difference in pressure. And whenever we have a difference in pressure, we know we have a pressure gradient. And these gas molecules will begin to move down their gradient from a high pressure to a low pressure. So as soon as the blood enters the capillary, we have this relatively thin wall that consists of the endothelium of the blood vessel, the capillary, the basement membrane, as well as the epithelium of our alveolus. And this entire layer allows our diffusion of these gas molecules. And this layer that consists of these three different things is known as the respiratory membrane inside the capillary that allows diffusion to take place.