<prompt> A 60-year old male pressents with progressivp difficulty in swallowing, vomiting and ocLsional regurgitation for the past 3 months. Barium studies showed marked dilatation of the upper esophagus with narrowmg of the lower segment. Manometry showed absent esophageal peristalsis. The pathogenesis of this condition is most likely related to-Reflux of gastric acid into the lower esophagusAbnormal dilatation of lower esophageal veinIncompetence of the lower esophageal sphincterAbsence of ganglion cells in the myenteric plexus of the esophagus  <response>: Hirschsprungs disease is a congenital disorder of the colon in which ceain nerve cells, known as ganglion cells, are absent, causing chronic constipation. The lack of ganglion cells is in the myenteric plexus Auerbachs plexus, which is responsible for moving food in the intestine. Ref Davidson edition23rd pg 796 