A correlative light microscopic, transmission and scanning electron microscopic study of the dorsum of human tongue.

The dorsum of the human tongue has three types of papillae, filiform, fungiform and circumvallate. Some investigators have studied these by light and transmission electron microscopy. Since knowledge of the morphology through studies by scanning of the morphology through studies by scanning electron microscopy (SEM) is scant, this investigation was started with the purpose of studying human tongues at different ages. One fetal tongue and portions of three tongues from newborns were removed. Additional specimens were biopsied from the anterior region of three adult tongues. Samples were processed routinely for light microscopy, transmission electron microscoy (TEM) and scanning electron microscopy (SEM). Two distinct features were evident on the fetal tongue. The first was that the surface epithelial layer of the tongue appeared to be periderm. The second was that fungiform papillae began their development earlier than filiform. At birth, the putative periderm had disappeared and a few filiform papillae were observed. On the adult tongue, filiform papillae were numerous and were comprised of two cell populations. One cell population contained numerous keratohyalin granules (KHG). The KHG were two types, eosinophilic and basophilic. Ultrastructurally, the eosinophilic granules were less electron dense and larger in size than the basophilic KHG.