2)development of esophagus and stomach (1 development of esophagus laryngotracheal diverticulum to stomach/th derived from primitive gut extending fror with the descent of the heart and lungs, it lengthens rapidly muscular coat, formed by surrounding mesenchyme /striated in upper two-thirds /smooth in lower one -third 食管2) development of esophagus and stomach ① development of esophagus ---derived from primitive gut extending from the laryngotracheal diverticulum to stomach ---with the descent of the heart and lungs, it lengthens rapidly ---muscular coat, formed by surrounding mesenchyme /striated in upper two-thirds /smooth in lower one-third