1.   An overstretched stomach causes the esophageal sphincter to open, allowing stomach acid to flow up.

2.   Dr. Timothy Wang, gastroenterologist at Massachusetts General Hospital, explains that the lower esophageal sphincter works like tightening a rubber band around a straw.

3.   If all else fails, surgery to tighten the esophageal sphincter has long been the treatment of last resort.

4.   One of the newest procedures, done through a laparoscope, involves wrapping a defective esophageal sphincter to strengthen it against reflux.

5.   Stomach acid is normally kept in the stomach by a muscular valve called the esophageal sphincter.

6.   The food is propelled into the esophagus, where contractions usher it down to the lower esophageal sphincter, which allows entry into the stomach.

7.   The other utterly basic remedy, says Callery, is to go easy on foods that contribute to reflux because they decrease the muscle tone in the esophageal sphincter.

8.   The ring, called the lower esophageal sphincter, then closes immediately to prevent the acid contents of the stomach from backing up into the esophagus.

9.   The problem lies in the muscle that plugs the stomach, called the lower esophageal sphincter.