Ultrastructural Study of the Relationship between the Morphogenesis of Filiform Papillae and the Keratinization of the Lingual Epithelium in the Mouse

Abstract

Tongues were removed from fetuses of mice on the 15th day of gestation (E15), from newborns (P0), and from juveniles on the 7th day (p7) and on the 21st day (P21) after birth for examination by light microscopy and transmission electron microscopy. In the fetuses at E15, no rudiments of filiform papillae were visible on the dorsal surface of the tongue. No evidence of keratinization was recognized throughout the entire dorsal lingual epithelium. At P0, rudiments of filiform papillae were compactly distributed over the dorsal surface, as are the filiform papillae in the adult, but their tips were rounder than those of the filiform papillae in the adult. Cell columns in the epithelium, with different degrees of keratinization of the type observed in the matured adult were indistinct. However, a keratinized layer was clearly visible on the tip of each filiform papilla. In juveniles at P7, the filiform papillae on the anterior part of the tongue were long and slender, and the anterior and posterior cell columns of the filiform papillae were identical to those in the adult. These results indicate that, in mice, the morphogenesis of filiform papillae advances in parallel with keratinization of the lingual epithelium from the stage just before birth to a stage a few weeks after birth.

Fine structure of the dorsal lingual epithelium in Tarentola annularis and Crocodylus niloticus

“…In majority of mammals, keratinisation of the epithelium begins with the appearance of the non-gustatory lingual papillae, namely, the filiform papillae, just before birth [21]. By contrast, the gustatory papillae, such as the fungiform, circumvallate and foliate papillae, appear at an earlier embryonic stage without any obvious relationship to the keratinisation of the lingual epithelium [19,30].…”

Fluorescence Immunohistochemistry by Confocal Laser-Scanning Microscopy for Studies of Semi-Ultrathin Specimens of Epoxy Resin-Embedded Samples

“…Morphogenesis of filiform papillae is closely related to the keratinization of the dorsal lingual epithelium (Iwasaki et al, 1999). Immunoreactivity specific for K13 and for K14 was not detected on the lingual epithelium of fetuses on day 15 after conception (E15), at which time the lingual epithelium was composed of a few layers of cuboidal cells.…”

Morphological study of lingual papillae in the fetal cat at mid-gestation, as revealed by light and scanning electron microscopy

“…1,2 Light and transmission electron microscopy demonstrated the absence of any rudiments of filiform papillae or signs of keratinization in the dorsal epithelium of the tongues of rats and mice in the middle or late period of gestation, whereas rudiments of filiform papillae can be clearly recognized in the dorsal epithelium of the tongue of newborn rats and mice just after birth. 3,4 Thus, the filiform papillae of rats and mice seem to develop rapidly and exclusively during the 2 or 3 days before birth, in parallel with keratinization of the epithelium.…”