Zenker diveiculum occurs at:
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
Upper esophageal spinchter
Lower esophageal sphincter
Both of the above
None of the above