GERD and Dysphagia - A vicious cycle
The upper esophageal sphincter relaxes during the pharyngeal phase of swallowing and is pulled open by the forward movement of the hyoid bone and larynx. This sphincter closes after passage of the food, and the pharyngeal structures then return to reference position. The pharyngeal phase of swallowing is involuntary and totally reflexive, so no pharyngeal activity occurs until the swallow reflex is triggered.
Esophageal phase: bolus is propelled downward by a peristaltic movement. The lower esophageal sphincter relaxes at initiation of the swallow, and this relaxation persists until the food bolus has been propelled into the stomach. Unlike the upper esophageal sphincter, the lower sphincter is not pulled open by extrinsic musculature. Rather, it closes after the bolus enters the stomach, thereby preventing gastroesophageal reflux. An interval of 8-20 seconds may be required for contractions to drive the bolus into the stomach.