Hi

The esophageal sphincter lies at the junction where the stomach and the esophagus join. Your stomach produces strong acids and enzymes (gastric juices) which are used in food digestion. The inner lining of your stomach has several mechanisms to protect itself from the effect of the gastric juices on itself, but the lining of the esophagus does not. There is a valve that stops the gastric juices from going up the esophagus - it is called the lower esophageal sphincter.

Thanks