Final answer:
Air entering and leaving the lungs through inspiration and expiration is known as ventilation, specifically pulmonary ventilation. It's part of the respiratory process but distinct from external and internal respiration, which are gas exchanges in the alveoli and tissues, respectively. Correct option is A.
Step-by-step explanation:
Air entering and leaving the lungs via inspiration and expiration is known as ventilation. This process, which is also termed pulmonary ventilation, involves moving air in and out of the lungs to facilitate gas exchange. When we inhale, oxygen-rich air is drawn into the lungs, whereas during exhalation, carbon dioxide-rich air is expelled.
This is distinct from external respiration, which refers to the gas exchange that occurs in the alveoli, and internal respiration, which refers to the exchange of gases within body tissues. Perfusion refers to the flow of blood in the pulmonary capillaries and is crucial for gas exchange as well; however, it is not synonymous with ventilation.