Ultrastructure of the surface epithelium cells in the basal (A), middle (B, C), and upper (D, E) regions of the corpus gastric pits and mucus structure (F).

<p>(A) Pit cells containing electron dense granules in their apical parts. Note the bundles of tonofilaments (arrow). (B) Cells with numerous electron-dense granules that form oval clusters in the supranuclear cytoplasm. (C) Cells with numerous granules that vary in electron density and aggregate with each other. (D) Degenerating cells with flattened nuclei and cytoplasm filled by the mucous mass. (E) Cells with destroyed apical regions. Note the mucus is partially released from the cell. (F) Mucus ultrastructure. Cell debris and fine fibrils are visible.