Taste bud morphology in the fetal and neonatal dog.

Light microscopy and scanning electron microscopy were used to examine tongues of beagle puppies at 38, 47, and 54 days of gestation (term = 63 days) and at postnatal ages ranging from birth to adulthood, to follow the time course of morphological maturation of the papillae and taste buds. Fungiform and circumvallate papillae were present on the 38th fetal day, although taste buds were not observed until the 47th fetal day. Large multipored buds and increasing taste bud numbers were noted from 47 days of gestation until birth. Keratinization of tongue epithelium, development of submucosal glands, deepening of the circumvallate trenches, and further increase in taste bud numbers occurred after birth. Anatomical findings indicate that the puppy's peripheral gustatory system is functional at birth but has not yet reached adult form. The presence of mature taste buds in the fetal dog suggests that it may be responsive to chemical stimuli at, or before birth.