The "limiting ridge" of the rat stomach

In the rat, the forestomach is separated from the glandular stomach by a fold of the forestomach mucosa which generates the "limiting ridge" on the inner surface of the organ. This ridge overlaps a deep groove which is flanked proximally by the forestomach and distally by the glandular stomach. Light microscopy and scanning electron microscopy reveal that the keratinized squamous epithelium of the forestomach merges into the columnar epithelium of the glandular stomach at the bottom of the groove. Among the columnar cells of the distal wall of the groove are numerous brush cells. A remarkably thick lamina muscularis mucosae extends deep into the ridge. The peculiar architecture of the "limiting ridge" and the presence of numerous brush cells in its distal wall suggest that the region not only represents the transitional zone between forestomach and glandular stomach but that it might have a more specific function.