Esophageal phase

The esophageal phase is the stage of swallowing in which a swallowed bolus is transported through the esophagus toward the stomach. It follows the pharyngeal phase, during which the bolus passes through the throat and enters the esophagus through the upper esophageal sphincter. The esophageal phase is largely involuntary and depends on coordinated muscular activity along the esophageal wall .^1,2

The main propulsive mechanism is peristalsis, a coordinated pattern of contraction and relaxation that progresses down the esophagus and moves the bolus toward the stomach. A swallow normally initiates this pattern, known as primary peristalsis. If material remains in or distends the esophagus, additional contractions called secondary peristalsis can occur without a new swallow, helping clear the remaining contents .¹

Movement of the bolus is coordinated with the lower esophageal sphincter, the high-pressure region between the esophagus and stomach. During swallowing, this sphincter relaxes before the approaching peristaltic wave reaches it, allowing the bolus to enter the stomach. It then returns toward its resting contracted state, helping maintain the barrier against reflux of stomach contents .¹

The esophageal phase differs from the pharyngeal phase in both location and function. The pharyngeal phase rapidly transfers the bolus through the throat while coordinating airway protection, whereas the esophageal phase primarily transports the bolus through the esophagus to the stomach. The two phases are nevertheless closely coordinated parts of a continuous swallowing process .^1,2