Figure 3
Esophagus of S. fuscus. (A) Mucosa with folds consisting of (a) cubic epithelium and (b) mucous glands; (B) mucosa with a tubular mucous secretory gland (arrow) and (c) muscle layer consisting of striated skeletal muscles; (C) esophagus sphincter; (D) ...
The sac-like stomach of S. fuscus is divided into the cardiac, fundic, and pyloric regions. In the cardiac, region the folds are lined with a simple cubic epithelium and lamina propria that branch off and form small secondary folds (Figure 4(A)). Mucous glands predominate in the lamina propria, which produce mucous to facilitate the passage of food. The muscular mucosa and submucosa are not evident. However, the muscular layer with the longitudinal tunica and the circular tunica is well developed. The last layer is a serous membrane with loose connective conjunctive tissue covered by a mesothelium. The gastric glands (Figures 4(B) and 5(C)), when present, are always located in the lamina propria and not in the submucosa.