The development of the esophageal and gastric mucosa in the gastroesophageal junction was studied in 61 fetuses of 13 - 41 weeks of the gestational age. During the 13th - 15th week, the esophageal multilayered epithelium was covered by a continuous layer of columnar mucous ciliated cells which were present only focally till the 25th week and disappeared later. Before the 15th week, the gastric mucosa was formed by pits only. The glands started as proliferating tubules in the basal parts of the pits in the 15th week. Further, they differentiated into oxyntic glands. The mucosa of the corpus was fully developed in the 27th week. The cardiac mucosa was absent in all the 10 fetuses examined between the 27th and 41st week of gestation. This supports the view that the gastric cardiac mucosa is not a physiological structure but that it results from glandular metaplasia of the distal esophageal mucosa due to gastroesophageal reflux.

        Key words: development of esophagus and stomach - cardia - gastroesophageal reflux - glandular metaplasia of the esophageal mucosa