What occurs during external respiration?

External respiration specifically refers to the gas exchange process that occurs in the lungs. During this process, oxygen is taken from the air in the lungs and diffuses into the blood in the surrounding capillaries, while carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the lungs to be exhaled. This exchange is driven by concentration gradients — oxygen at a higher concentration in the alveoli compared to the blood, and carbon dioxide at a higher concentration in the blood compared to the alveoli.

The correctness of the selected answer reflects the dual role of external respiration: the uptake of oxygen and the removal of carbon dioxide. Understanding this mechanism is critical, as it underscores the importance of alveolar function and the respiratory process in maintaining efficient gas exchange, which is vital for cellular respiration and overall metabolic function.