Which structure is part of the lower respiratory tract?

• A. Nose
• B. Trachea
• C. Pharynx
• D. Larynx

Answer: (B)

The lower respiratory tract includes the airways that conduct air down toward the lungs and participate in gas exchange, such as the trachea, bronchi, and lungs. The nose, pharynx, and larynx are part of the upper airway, handling filtration and conditioning of air (and in the larynx, voice). The trachea sits below the larynx and serves as the main conduit to the bronchi and lungs; it’s supported by cartilage rings to stay open and lined with cilia and mucus to trap and move particles out. Because it is a central conducting passage toward the lungs, the trachea is the correct choice for a structure that is part of the lower respiratory tract. The other options are part of the upper airway.