What process involves moving air in and out of the alveoli during one complete breath?

Ventilation is the process that encompasses the movement of air into and out of the alveoli, the tiny air sacs in the lungs where gas exchange occurs. This process is fundamental for ensuring that oxygen enters the bloodstream and carbon dioxide is expelled from the body.

During ventilation, two key actions take place: inspiration and expiration. Inspiration refers to the act of drawing air into the lungs, while expiration involves expelling air out of the lungs. Together, these steps facilitate the overall process of ventilation, which maintains adequate gas exchange and regulates the levels of oxygen and carbon dioxide in the blood.

Diffusion, on the other hand, refers to the movement of molecules from an area of higher concentration to one of lower concentration, which specifically pertains to the exchange of gases between the alveoli and the blood. Perfusion describes the movement of blood through the pulmonary capillaries surrounding the alveoli, allowing for the actual exchange of gases that have entered the alveoli through ventilation. Therefore, while diffusion and perfusion are crucial for respiratory function, they do not describe the mechanical process of air movement as ventilation does.