Which phase is defined by peristaltic transport of the bolus through the esophagus with relaxation of the lower esophageal sphincter?

• A. Esophageal phase
• B. Oral phase
• C. Pharyngeal phase
• D. None of the above

Answer: (A)

Swallowing progresses through three phases, and the esophageal phase is the one where the bolus is moved down the esophagus by coordinated peristaltic waves while the lower esophageal sphincter relaxes to allow entry into the stomach. Primary peristaltic contractions propel the bolus downward, and the transient relaxation of the LES opens the gateway to the stomach. If any material lingers, secondary peristalsis can clear it. The oral phase is mainly tongue-driven and does not involve the LES, while the pharyngeal phase focuses on airway protection and initiating the swallow reflex. Therefore, the scenario described—peristaltic transport through the esophagus with LES relaxation—belongs to the esophageal phase.