Final answer:
The two basic requirements for gas exchange are ventilation, the movement of air in and out of the lungs, and perfusion, the blood flow in the pulmonary capillaries.
Step-by-step explanation:
The two basic requirements for gas exchange are ventilation and perfusion. Ventilation is the process of moving air into and out of the lungs, ensuring that there is a high partial pressure of oxygen in the alveoli. Perfusion involves the flow of blood in the pulmonary capillaries, where blood low in oxygen and high in carbon dioxide undergoes gas exchange with the air in the lungs. For efficient gas exchange, the volumes of air and blood must be compatible. Diffusion of gases occurs according to their partial pressure gradients, from areas of high pressure to areas of low pressure.