Which process describes the exchange of CO2 and O2 between the lungs and the blood?

• A. Internal Respiration
• B. Transrespiratory Pressure
• C. Atmospheric Pressure
• D. External Respiration

Answer: (D)

Gas exchange between the lungs and the blood occurs at the alveolar membranes, where oxygen moves from the air in the alveoli into the blood and carbon dioxide moves in the opposite direction to be exhaled. This is external respiration, driven by the partial pressure gradients of O2 and CO2 across the alveolar-capillary barrier.

Internal respiration refers to gas exchange between the blood and body tissues, with O2 moving from blood to tissues and CO2 from tissues to blood.

Transrespiratory pressure is the difference between airway pressure and atmospheric pressure that drives airflow, not the actual exchange of gases at the membrane.

Atmospheric pressure is the ambient pressure of the surrounding air and serves as the baseline for breathing, but it does not describe the gas exchange process itself.