Study by scanning electron microscopy of the morphogenesis of three types of lingual papilla in the mouse.

Tongues were removed from fetuses of mice on the 15th day of gestation (E15), from newborns (P0), from juveniles on the 7th day (P7) and on the 14th day (P14) after birth for examination by scanning electron microscopy. In the fetuses at E15, rudiments of fungiform papillae with a relatively regular, lattice-like pattern were visible on the anterior half of the dorsal surface of the tongue. The outline of the rudiment of a circumvallate papilla could be recognized on the median line between the lingual body and the lingual radix. No rudiments of filiform papillae could be seen. At P0, rudiments of filiform papillae were compactly distributed over the dorsal surface, as are the filiform papillae in the adult, their width was approximately one-third of that of fungiform papillae, and their tips were rounded than those of the filiform papillae in the adult. The fungiform papillae then increased in size and became somewhat irregular in shape. In juveniles at P7, the filiform papillae were long and slender, being relatively large on the intermolar eminence. A taste pore was visible in the center of each fungiform papilla at this stage. The shape of the circumvallate papilla was similar to that in the adult. In juveniles at P14, the shapes of all three types of papilla were almost the same as those in the adult. The rudiments of each of the three kinds of lingual papilla appeared at a different stage of development of mice; rudiments of the fungiform and circumvallate papillae, which are related to the sense of taste, were formed earlier than those of the filiform papillae, which are not involved in taste.