Age-related characteristics of gastric squamous epithelial mucosa in foals.

Specimens of grossly normal gastric stratified squamous epithelial mucosa adjacent to the margo plicatus on the right side and along the greater curvature were obtained from 7 foetuses, 10 term foals and 12 foals 2-35 days old. Gastric squamous epithelium from the foetuses changed markedly during gestation. At 150-270 days, the epithelium was 8-10 cells thick, with a single layer of basal cells. Epithelial cells were polyhedral and had abundant clear or slightly stained cytoplasm. In the 300-day foetus the basal layer was thicker, epithelial cells were polyhedral, and there was a flattened 1 cell-thick layer superficially. In the 335-day foetus, the epithelial cells were flat and there was a superficial layer of keratinised cells, 1-2 cells thick. In term foals, the gastric epithelium consisted of 10-12 cell layers, with 4-5 thin layers of surface keratin. Epithelial projections (papillae) were either absent or not pronounced. The gastric epithelium became thicker with increasing age, including increased epithelial cell layers, thickening of the keratinised layers, and more pronounced papillae. Desquamation was observed in the keratinised layers of gastric squamous epithelium from foals > or = 2 days of age.