What type of gas exchange occurs in the alveoli?

The correct answer is that external respiration occurs in the alveoli. This process is fundamental to the respiratory system, involving the exchange of gases between the air in the alveoli and the blood in the surrounding capillaries.

During external respiration, oxygen is transferred from the air in the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli to be exhaled. This gas exchange is critical as it helps maintain the body’s oxygen levels and remove carbon dioxide, which is a waste product of cellular metabolism.

Understanding why this process is labeled as external respiration lies in the distinction between internal and external respiration. External respiration refers specifically to the exchange of gases occurring in the lungs, whereas internal respiration occurs at the cellular level when oxygen is utilized for energy production and carbon dioxide is released as a byproduct. Choosing this answer reflects an understanding of the specific location and context of the gas exchange that happens within the lungs.

As for the other options: cortical respiration is not a recognized term related to gas exchange, and cellular respiration refers to the metabolic processes that occur within cells rather than the external gas exchange happening in the lungs. Thus, the selection for external respiration emphasizes the correct physiological process that takes place in the alveoli.