Microvasculature of the dorsum of the rat tongue: a scanning electron microscopic study using corrosion casts

The purpose of this study was to examine the microvascular system of the dorsum of the rat tongue in relation to the subepithelial connective tissue relief. Methylmethacrylate corrosion casts of the vasculature as well as specimens in which the epithelium had been removed were prepared and examined by scanning electron microscopy (SEM). The SEM images revealed four distinct layers in the vasculature of the lamina propria. Superficially, Layer 1 comprised the irregularly shaped ends of capillary loops. Layer 2 consisted of parallel ascending and descending capillaries. These two layers were drained by the subjacent Layer 3, a fish-net-like venous plexus. More deeply, Layer 4 contained arterioles ascending from the muscular layers of the tongue. The vessels of larger papillary structures formed cylindric networks supplied by several arterioles and drained through a single venule to the venous plexus in Layer 3. At their base, the capillary loops often showed a constriction, suggestive of a sphincter. Arteriovenous anastomoses were rare. The epithelium-connective tissue interface showed short conical papillae as well as larger papillary structures which corresponded in both distribution and size to the capillary loops found in the vascular casts. The results confirm that the tongue is highly vascularized and demonstrate that the vascular supply to the papillae, taste buds, and other surface structures forms a highly organized and specific system which is adapted to the specific functions of this organ in the rat.