Which structures are part of the lower airway?

The correct answer encompasses the primary components of the lower airway, which include the larynx, trachea, and bronchi. These structures are vital in the respiratory process. The larynx acts as a passageway for air to enter the trachea and is also involved in phonation. The trachea, commonly known as the windpipe, extends from the larynx and splits into two primary bronchi, which branch into smaller bronchi and ultimately lead to the lungs.

This configuration allows for the effective conduction of air to the alveoli, where gas exchange occurs. In contrast, the other options consist of structures primarily located in the upper airway or other systems not directly classified as part of the lower airway. For example, the nose, mouth, and pharynx are involved in the initial stages of respiratory function, such as filtering, warming, and humidifying air, but they do not fall under the classification of the lower airway. The pharynx, while being part of the respiratory system, is mainly located between the nasal cavity and the larynx. Additionally, the inclusion of the diaphragm in one of the choices pertains more to the mechanics of breathing rather than being an airway structure.