Structures of the lower airway include all of the following, EXCEPT which?

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

Answer: (B)

The part of the airway involved in moving air down toward the lungs and conducting it to the gas-exchange tissues is the lower airway. This includes the trachea, the bronchi and bronchioles, and the alveoli where oxygen and carbon dioxide are exchanged. The epiglottis, however, belongs to the upper airway; it sits at the entrance to the larynx and helps protect the airway by covering the glottis during swallowing. It’s not a site where air is conducted deeper into the lungs or where gas exchange occurs, so it isn’t considered a lower airway structure. That’s why the epiglottis is the exception here. The other listed structures—alveoli, trachea, and bronchioles—are all part of the lower airway and play direct roles in air movement and gas exchange.