The Protection of the Laryngeal Airway during Swallowing

The protection of the larynx during swallowing depends upon a number of factors: (1) The epiglottis acts as a ledge to check the descent of the bolus, thereby obviating the necessity for early closure of the larynx. (2) Elevation of the larynx results in the lumen of the laryngeal vestibule being narrowed and arched backward. (3) The bulk of the bolus is normally deviated to one or both sides of the larynx, down the lateral food channels. (4) When the bolus is passing down the lateral food channels, the vestibule may be still open and in communication with air in the hypopharynx. Barium often enters the vestibule at this stage. (5) The epiglottis is bent downward to form a hood over the entrance to the larynx, but is not closely applied to the entrance to the larynx until the last of the bolus leaves the pharynx. (6) Closure of the larynx is effected by contraction of the sphincteric girdle of muscle which surrounds it, and can occur without the need for the larynx being raised. The larynx may be closed at any stage during the act of swallowing. Complete closure is always effected when the last of the bolus leaves the pharynx; any barium which has entered the vestibule of the larynx is squeezed out at this stage. (7) The epiglottis prevents the deposition of a residue of food over the entrance to the larynx and upon reinflation of the airway carries the residue upwards into the vallecula. (8) If the epiglottis be removed reinflation of the airway is delayed until all traces of food have been removed from the entrance to the larynx by repeated acts of swallowing.