Three-dimensional architecture of the connective tissue core and surface structures of the lingual papillae in the rabbit.

Three-dimensional characteristics of the epithelial cell layer and connective tissue interface of the tongue were studied using scanning electron microscopy. In this study, the fragments of tongue were fixed in modified Karnovsky's fixative solution. Subsequently, the specimens were treated with 10% NaOH solution for 4-7 days at room temperature and postfixed in 1% OsO4 in 0.1 M phosphate buffer (pH 7.4) for 2 hours at 4 degrees C. They were dehydrated through a graded ethanol series, and critical-point dried with CO2. The specimens were coated with gold and observed in a scanning electron microscope, JEOL JSM-6100. The results showed numerous papillae on the dorsal surface of the tongue divided into four groups (filiform, fungiform, foliate and vallate papillae). Filiform papillae are conically shaped; fungiform papillae have an irregular round surface; foliate papillae are oval in shape and have some parallel projections; and vallate papillae are located in the posterior part of the tongue and have a depression around the center. After the treatment with 10% NaOH solution, the original arrangements of connective papillae could be seen. This characteristic three-dimensional distribution of the collagen fiber bundles is typical for each superficial papillae depending on whether it is filiform, fungiform, foliate or vallate.