Which statement correctly differentiates the conducting airways from the respiratory zone?

Which statement correctly differentiates the conducting airways from the respiratory zone?

• A. Conducting zone includes trachea, bronchi, bronchioles—conduct air and condition it; respiratory zone includes respiratory bronchioles, alveolar ducts, alveoli—site of gas exchange
• B. Conducting zone includes alveoli; respiratory zone includes trachea
• C. Gas exchange occurs in the conducting zone
• D. There is no functional distinction between zones

Answer: (A)

The main idea here is the functional split of the airways into a conducting zone and a respiratory zone. The conducting zone, from the trachea through the bronchi and bronchioles up to the terminal bronchioles, serves to bring air to the lungs and condition it—warming, humidifying, and filtering it as it travels. The respiratory zone begins at the respiratory bronchioles and includes the alveolar ducts and alveoli, where gas exchange actually occurs. The alveolar walls, with their thin membranes and close contact with capillaries, provide the large surface area and short diffusion distance needed for oxygen to enter the blood and carbon dioxide to exit. That organizational pairing—air transport and conditioning in the conducting zone, gas exchange in the respiratory zone—makes the statement correct.

The main idea here is the functional split of the airways into a conducting zone and a respiratory zone. The conducting zone, from the trachea through the bronchi and bronchioles up to the terminal bronchioles, serves to bring air to the lungs and condition it—warming, humidifying, and filtering it as it travels. The respiratory zone begins at the respiratory bronchioles and includes the alveolar ducts and alveoli, where gas exchange actually occurs. The alveolar walls, with their thin membranes and close contact with capillaries, provide the large surface area and short diffusion distance needed for oxygen to enter the blood and carbon dioxide to exit. That organizational pairing—air transport and conditioning in the conducting zone, gas exchange in the respiratory zone—makes the statement correct.