reference "Esophagus - anatomy and development" "Esophagus - anatomy and development" http://www.nature.com/gimo/contents/pt1/full/gimo6.html "Esophagus - anatomy and development" GI Motility online "Esophagus - anatomy and development" "Esophagus - anatomy and development" "Esophagus - anatomy and development" Esophagus - anatomy and development : GI Motility online "Esophagus - anatomy and development" "Esophagus - anatomy and development" Esophagus - anatomy and development