Morphological and histological studies on the gastric mucosa of the Japanese field vole,Microtus montebelli montebelli.

The gastric mucosa of herbivorous field voles was examined with the naked eyes, a light microscope, and a scanning and a transmission electron microscope. Its morphological characteristics were compared with those of omnivorous golden hamsters. The stomach of the hamster consists of two parts, forestomach and glandular stomach, whereas that of the field vole is composed of three parts, esophageal sac, fundic stomach and pyloric stomach. The fundic stomach has a number of gastric glands which open by oval pits on the mucosal smooth surface. The esophageal sac mucosa and the pyloric stomach mucosa are connected with each other on the side of the lesser curvature, both the mucosal membranes being lined with stratified squamous epithelia. The mucosal surface of the esophageal sac has numerous complicated folds, whereas that of the pyloric stomach has a succession of regularly and compactly arranged protrusions. A fimbria, specific to the field vole, is observed between the esophageal sac and the fundic stomach, making a definite distinction of these two parts. The fimbria appears to strengthen the function of the esophageal sac as a fermental vat. The pyloric gland region is separated from the fundic stomach by the pyloric stomach and is located at the short part just before the duodenum. The functional roles of the pyloric stomach and the pyloric gland segment are not clear.