Three-dimensional architecture of the connective tissue core of the lingual papillae in the guinea pig.

The three-dimensional structure of the connective tissue core (CTC) of the lingual papillae of the guinea pig was studied by means of scanning electron microscopy, after fixation with Karnovsky's fixative and after removal of the epithelial cell layers by long-term treatment with hydrochloric acid. The CTC of four types of lingual papillae was revealed. (a) Filiform papillae distributed over the anterior part (comprising about one half of the tongue) are characterized by having a few long connective tissue protrusions arranged transversely to the long axis of the tongue, while large conical papillae distributed on the intermolar prominence (intermediate part comprising most of the posterior half of the tongue) have more numerous and longer connective tissue protrusions, forming a bundle. (b) Fungiform papillae scattered among the filiform papillae are restricted to the anterior part of the tongue and possess connective tissue components in the form of a "fist-like" structure. (c) Foliate papillae are found in lateral and posterior locations. At both sites they contain slender epithelial crypts. Removal of the epithelia reveals wide grooves which correspond to the epithelial crypts. The rims of these grooves are surrounded by numerous small protrusions.