Scanning electron microscopical studies of developing gustatory papillae in humans

Development and morphological changes of human gustatory papillae during postovulatory weeks 6-15 have been studied using scanning and transmission electron microscopy. The first papilla of the tongue appears around postovulatory week 6 in its caudal midline near the foramen caecum. In contrast, the dorsal epithelium of the anterior part of the tongue shows only small hillock- or papilla-like elevations from week 6 on, which comprise an aggregation of 5-20 epithelial cells. From week 7 on, most prominent fungiform papillae develop near the median sulcus and at the margins of the anterior part of the tongue. At their tops, the first primitive taste pores are found around week 10; these are often covered with processes of adjacent epithelial cells. Most pores, however, develop around weeks 14-15. The maturation of taste buds does not coincide with the appearance of taste pores, since taste bud cells are not fully differentiated in the observed period of time. Fungiform papillae are developed before filiform papillae, which do not occur within the first 15 weeks of gestation. Fungiform papillae tend to grow between weeks 8 and 15 of gestation, whereas the size of vallate papillae seems to be constant during this period.