Which part of the lower airway is defined as the area from the trachea to terminal bronchioles?

• A. Respiratory zone
• B. Conducting zone
• C. Exchange zone
• D. Inflammatory zone

Answer: (B)

The conducting zone encompasses the region of the lower airway that spans from the trachea down to the terminal bronchioles. This segment is primarily responsible for the transportation of air into the lungs without participating in gas exchange. It includes structures such as the trachea, bronchi, and bronchioles, all of which function to warm, humidify, and filter the inhaled air. The conducting zone is crucial in preparing air for the gas exchange process that occurs in the respiratory zone, which consists of the respiratory bronchioles, alveolar ducts, and alveoli.

On the other hand, the respiratory zone, which is defined as the area where gas exchange occurs, includes the structures beyond the terminal bronchioles, such as the alveoli. The term "exchange zone" is not commonly used in pulmonary physiology; the correct terminology associates it with the respiratory zone. The inflammatory zone does not refer to a specific anatomical area in the lower airway and is instead a conceptual term that may be used in various contexts related to respiratory pathology.