What structures are defined as the lower airway?

The lower airway is defined as the part of the respiratory system that begins at the trachea and includes structures that are involved in the passage of air and gas exchange. This includes the trachea, which is the windpipe leading to the bronchi, then extending into the bronchi, bronchioles, and finally reaching the alveoli, where the exchange of oxygen and carbon dioxide takes place.

The trachea serves as the main conduit for air entering the lungs, dividing into the right and left bronchi, which further branch into smaller bronchioles that end in the alveoli. This entire section of the respiratory system is crucial for the effective functioning of breathing and gas exchange.

In contrast, the other options include structures that do not fall within the lower airway definition. The nose and pharynx comprise the upper airway, primarily involved in filtering, humidifying, and warming the air before it reaches the lower airway. The pharynx and larynx are also part of the upper airway; the larynx, while important for voice production and protecting the trachea during swallowing, does not include the structures that are primarily responsible for gas exchange. The sinuses and throat are further indications of upper airway components and are