Which sphincter relaxes during swallowing to allow food entry into the stomach?

• A. Pyloric sphincter
• B. Lower esophageal sphincter
• C. Upper esophageal sphincter
• D. Anal sphincter

Answer: (B)

During swallowing, the lower esophageal sphincter relaxes transiently to allow the bolus to move from the esophagus into the stomach. This relaxation is a controlled, short-lived opening that follows the swallowing reflex, after which the sphincter tightens again to prevent backflow. The other sphincters aren’t responsible for letting food into the stomach: the upper esophageal sphincter mainly opens to admit the food into the esophagus, the pyloric sphincter regulates passage from the stomach to the duodenum, and the anal sphincter is involved in continence and defecation.