Which structures comprise the lower respiratory system?

• A. Nose and nasal cavity
• B. Pharynx and larynx
• C. Larynx, trachea, bronchi, bronchioles, alveoli
• D. Alveoli only

Answer: (C)

The lower respiratory system consists of the structures that carry air from the larynx down to the lungs and where gas exchange ultimately occurs. It includes the larynx, trachea, bronchi, bronchioles, and the alveoli. The nose and nasal cavity are part of the upper tract and mostly handle filtration, warming, and humidifying inhaled air, while the alveoli are the sites of gas exchange within the lungs. The full set from the larynx through the alveoli best represents the lower respiratory system, rather than just the alveoli alone or the upper airways.