Electron microscopic study on the esophageal mucosa in human fetuses

Morphogenetic studies of the esophageal mucosa in human fetuses have been few and there is only one report at the ultrastructural level. We thus studied the esophageal mucosa in human fetuses (at the gestational ages from the 7th to 21st week) by scanning (SEM) as well as transmission electron microscopy (TEM). Our results and the review of the literature lead to the following conclusions: 1) Primary cilia were seen in the 7th and 8th week of gestation. 2) Ciliated cells appeared around the 8th week of gestation. They increased in number according to the fetal ages, but gradually decreased after the 14th week of gestation. Their degenerative process at the ultrastructural level was similar to that reported previously. 3) The stratified squamous epithelia appeared at the 14th week of gestation, but the squamous cells remained immature even at the 21st week. 4) Glycogen granules in non-ciliated cells decreased as the differentiation of the cells proceeded, suggesting that they provide an energy source necessary for the cell differentiation.