The lower airway divides into what two functional zones?

• A. Inspiratory zone and expiratory zone
• B. Conducting zone and respiratory zone
• C. Aeration zone and circulation zone
• D. Ventilatory zone and perfusion zone

Answer: (B)

The correct response identifies the two functional zones of the lower airway as the conducting zone and the respiratory zone. The conducting zone is responsible for transporting air to the sites of gas exchange and includes structures such as the trachea, bronchi, and bronchioles. This zone does not participate in gas exchange; instead, its primary role is to condition the air (warming, humidifying, and filtering) before it reaches the respiratory zone.

The respiratory zone, on the other hand, is where gas exchange occurs. This includes the alveoli and the respiratory bronchioles. In this area, oxygen enters the blood, and carbon dioxide is expelled. The two zones work together to ensure that air is effectively brought into the lungs and that the vital process of gas exchange can happen efficiently.

Understanding the distinction between these two zones is fundamental to grasping how the respiratory system operates and how various pathological conditions can affect each part. For instance, in conditions like asthma, the conducting zone can become obstructed, while pneumonia can directly impact the respiratory zone.