Structures of the lower airway include all of the following, EXCEPT:

• A. The trachea.
• B. Bronchioles.
• C. The epiglottis.
• D. Alveoli.

Answer: (C)

Understanding which structures belong to the lower airway helps distinguish where air travels versus where protection or other functions occur. The lower airway consists of the trachea, the bronchi and bronchioles, and the alveoli—the passageway that conducts air down to the lungs and the sites of gas exchange. The epiglottis, on the other hand, sits at the entrance to the airway and serves to protect the lower airway by covering the glottis during swallowing; it is part of the upper airway. So the epiglottis is not a lower airway structure, making it the correct choice. The trachea, bronchioles, and alveoli all fit within the lower airway.