The trachea is part of the lower airway and, like the esophagus, begins at vertebral level CVI, where it is continuous with the larynx above (Fig. 8.178B). The trachea lies directly anterior to the esophagus and passes inferiorly in the midline to enter the thorax.
The pharynx is a common pathway for air and food, and the head with similar compartments in the lower neck (see pp. 1029–1041).