Gastroesophageal reflux disease (GERD) is a digestive disorder. It involves the esophagus, the tube that carries food from your mouth to your stomach.
In GERD, acid and digestive enzymes from the stomach flow backwards into the esophagus. This backward flow of stomach juices is called "reflux". These caustic stomach juices inflame the lining of the esophagus. This causes heartburn and other symptoms. If GERD is not treated, it can permanently damage the esophagus.
A muscular ring seals the esophagus from the stomach. This ring is called the esophageal sphincter. Normally, the sphincter opens when you swallow, allowing food into your stomach. The rest of the time, it squeezes tight to prevent food and acid in the stomach from backing up into the esophagus.
In most people with GERD, however, the esophageal sphincter does not seal tightly. It remains relaxed between swallows. This allows digestive juices to enter the esophagus and irritate the esophageal lining.
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