The functions of the esophagus are to transport swallowed boluses to the stomach and to prevent gastroesophageal reflux. For the former function, esophageal peristalsis is of paramount importance, whereas for the latter a properly functioning lower esophageal sphincter (LES) is required. Under normal circumstances, the LES acts in concert with the portion of the diaphragm (right crus) that surrounds it.