The process of gas exchange in the pulmonary alveolus?

The pulmonary alveolus are the small sacs of air in the lungs. It is here that the exchange of oxygen and carbon dioxide take place between the lungs and the capillary beds of the bloodstream. The capillary beds are extremely thin, only one cell thick, so the gases easily p through - oxygen from the lungs into the blood to be circulated throughout the body, and carbon dioxide from the blood into the lungs to be exhaled.