Gastroesophageal reflux disease (GERD) is a chronic digestive disease that occurs when stomach acid or, occasionally, bile flows back (refluxes) into your food pipe (esophagus). The backwash of acid irritates the lining of your esophagus and causes GERD signs and symptoms.
In normal digestion, once we eat, food travels from mouth to stomach through a tube called the esophagus. At the lower end of the esophagus is a small ring of muscle called the lower esophageal sphincter (LES). The LES acts like a one-way valve, allowing food to pass through into the stomach. Normally, the LES closes immediately after swallowing to prevent back-up of stomach juices, which have a high acid content, into the esophagus.
GERD occurs when the LES does not function properly allowing acid to flow back and burn the lower esophagus. This irritates and inflames the esophagus, causing heartburn and eventually may damage the esophagus.