Figure 1.

Salient features of the normal swallowing mechanism. A: The transported portions of processed (solid) food keep accumulating on the pharyngeal surface of the tongue and in the valleculae, and the bolus in the oropharynx enlarges with each transport cycle. The duration of bolus aggregation may range from a fraction of a second to 10 seconds. B: During the pharyngeal phase, the nasal cavity oral cavity and larynx are sealed off, and the bolus is advanced through the pharynx and into the esophagus by pharyngeal peristalsis. C: Airway protection is an essential feature of swallowing and is multitiered. Airway protection includes adduction of the true vocal cords, vertical approximation of adducted arytenoids, tilting back of the epiglottis closing the laryngeal vestibule, tucking of the sealed airway under the base of the tongue away from the bolus path, and neuronal suppression of respiration while the bolus is passing through the pharynx. D: Once the bolus is passed on to the esophagus, the airway returns to its open state. The oropharyngeal phase of swallowing begins with adduction of the vocal cords and ends with a return to their normal position.