Zenker diveiculum occurs at:
Upper esophageal spinchter
Lower esophageal sphincter
Both of the above
None of the above
Diveicula of the esophagus are mainly located above the LES (epiphrenic diveiculum) or the UES (pharyngoesophageal--or Zenker--diveiculum). They are both caused by abnormalities involving the LES or the UES, which result in protrusion of the mucosa and submucosa through the muscular layers