Which of the following is a function of the trachea and bronchial tree?

• A. Gas exchange in the alveoli
• B. Airway conduction, protection and filtration, air distribution, conditioning air, and structural support
• C. Endocrine hormone production
• D. Blood filtration by the kidneys

Answer: (B)

The trachea and bronchial tree serve as the conducting airways that move air into the lungs while also conditioning and protecting it. They don’t perform gas exchange—that happens in the alveoli where oxygen moves into the blood and carbon dioxide is released. They also aren’t involved in endocrine hormone production or kidney-based blood filtration.

This system conducts air to the deeper lungs, protects and filters it with mucus and cilia to remove particles, distributes air evenly through the branching passages, warms and humidifies the air to bring it closer to body conditions, and provides structural support with cartilage to keep the airways open. That combination of conduction, protection/filtration, distribution, conditioning, and structural support best matches the functions of the trachea and bronchial tree.