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Lower Esophageal Sphincter


Updated September 11, 2007


The muscle between the esophagus and stomach. When a person swallows, this muscle relaxes to let food pass from the esophagus to the stomach. It stays closed at other times to keep stomach contents from flowing back into the esophagus.

Pronunciation: LOH-wur uh-saw-fuh-JEE-ul SFEENK-tur
Also Known As: LES
GERD occurs when the lower esophageal sphincter (LES) does not close properly and stomach contents leak back, or reflux, into the esophagus.
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