The LES, a zone of tonically contracted smooth muscle surrounding the distal esophagus. Is innervated by vagal nerves and receives signals from multiple organs. A defect in this neural control may result in a dysfunctional LES with periods of transitory spontaneous relaxation. These periods of relaxation allow gastric contents to reflux back into the esophagus. In addition, the esophagus traverses both the abdominal and thoracic cavities. With the LES positioned strategically between the two. Most of the LES is abdominal. The greater the length of intraabdominal esophagus. The more competent this becomes. Any condition that shortens the abdominal valve segment of the LES will increase the likelihood of reflux.