Definition: The LES, which stands for lower esophageal sphincter, is the band of muscle between the esophagus and stomach. It acts as a sort of valve to control the flow into and out of the stomach.
When a person swallows, this muscle relaxes to let food pass from the esophagus to the stomach. It normally stays closed at other times to keep stomach contents from flowing back into the esophagus.
However, in people who have a condition known as GERD, the LES stays open longer than it should, allowing stomach contents to flow back into the esophagus, and irritating the esophageal lining tissues. This can not only result in symptoms such as heartburn, but also can worsen asthma symptoms.
Also Known As: lower esophageal sphincter
Examples: GERD occurs when the LES does not close properly and stomach contents leak back, or reflux, into the esophagus. In people with asthma, this can cause asthma symptoms.
