The dorsal part of the common foregut and the normal esophagus were negative for PAS. FGF7, 10 were expressed on the places where the PAS staining were positive.

• PAS染色及FGF7、10免疫组化染色可见前肠背侧半及食管为阴性,前肠腹侧半及气管部分为阳性;