Pharyngeal Phase

 

 

Both pharyngeal and esophageal phases of swallowing are under involuntary neuromuscular control.  

 

The bolus will be formed by the tongue pressing the masticated food against the hard palate while the extrinsic lingual muscles push the bolus backwards.  At the area of the palatoglossal folds (also called the Anterior Pillars of the Fauces or anterior tonsilar pillars), the pharyngeal phase of swallowing is initiated.  In addition to the bolus contacting the anterior pillars, posterior tongue movement and stimulation of the pharyngeal mucosa  and wall, are thought to stimulate the swallowing reflex.  Stimulation of the internal branch of the superior laryngeal nerve can independently trigger the swallow reflex.  

 

 

 

The sequential steps to pharyngeal phase of swallowing are:

  1. Velum elevating to contact posterior pharyngeal wall and block upward movement of bolus into nasopharynx (called velopharyngeal port valving)

  2. Elevation of the larynx and hyoid bone toward base of tongue, bringing a passive flipping over of the epiglottis to cover the glottis (opening to the larynx and trachea)

  3. Contraction of pharyngeal constrictor muscles from superior to inferior direction

  4. Opening (relaxation) of cricopharyngeal sphincter (also called the upper esophageal sphincter) to allow passage of bolus into esophagus

 

 

 

The pharyngeal phase of swallowing lasts approximately 1 second.