Histology of the stomach in the Caucasian squirrel, a scanning electron microscope and immunohistochemical study.

This study was performed to investigate the gross anatomy, histochemistry, and immunohistochemistry of the stomach in the Caucasian squirrel. A total of five male squirrels were included. The obtained results showed that the shape of the stomach was acutely crescent and consisted of four regions namely; cardiac, fundus, body, and pylorus. The stomach glandular and its wall was consisted of four layers; serosa, muscularis, submucosa, and mucosa. All part of the mucosa was covered by a simple columnar epithelium. Furthermore, gastric glands were of the simple tubular type. The mucous cells of the fundic and body regions were PAS-positive. In the lower third of the gastric glands, parietal, and chief cells were identified. The number of chief cells was increased toward the pyloric area. Scanning electron microscopy showed that the fundus region contained many plicae and grooves and each plica carried numerous glands opening. In the body region, cells were polygonal and formed network-like structures. In the pyloric region, a mucosal ridge between the body and antrum and a thick mucosal crest on the lesser curvature were identified. Immunohistochemical staining showed that Sox9 was strongly expressed in the fundic region, however, its expression in the body and pylorus was moderate to weak. In conclusion, there are some similarities and differences between the stomach of the Caucasian squirrel and other mammals including rodents. The obtained results may enhance our basic knowledge regarding the feeding habits and digestive system histophysiology of this species.