What is the role of the esophageal sphincters in digestion?

• A. To regulate entry of food into the stomach.
• B. To prevent backflow of stomach contents.
• C. To prevent backflow of stomach contents and regulate entry of food into the stomach.
• D. To secrete mucus to protect the esophagus.

Answer: (C)

The esophageal sphincters act as gates that coordinate movement between the esophagus and stomach and protect the esophagus from stomach contents. The lower esophageal sphincter opens to allow the swallowed bolus into the stomach and then tightens to prevent backflow of stomach contents into the esophagus. This dual role—regulating entry into the stomach and stopping reflux—best captures what these sphincters do. The idea of mucus secretion isn’t a function of the sphincters, since mucus is produced by the mucosal lining and glands, not by the sphincter muscles.