In the esophageal phase, what stimulates the first peristaltic wave which moves the bolus into the cervical esophagus?

• A. Food bolus moving through
• B. Bolus entering stomach
• C. A meal beginning
• D. Mechanical stimulation of the esophagus

Answer: (A)

During the esophageal phase, the first peristaltic wave is triggered by the arrival and distension of the food bolus in the esophagus. This mechanical stretch activates esophageal mechanoreceptors, initiating a vagal reflex that generates a coordinated wave of contractions to propel the bolus into the cervical esophagus. The presence and movement of the bolus itself is the immediate stimulus for that first peristaltic wave. Bolus entering the stomach or the meal starting are downstream events or non-specific triggers, and while mechanical stimulation underlies the process, the most specific trigger described here is the bolus moving through the esophagus.