Fine structure of taste buds located on the lamb epiglottis.

BACKGROUND Taste buds located on the aryepiglottal folds and laryngeal surface of the epiglottis are the principal receptors responsible for the initiation of the laryngeal chemoreflex. In contrast to the wealth of information available concerning the ultrastructure of oral taste buds, little comparable data exists for taste buds located at the entrance to the larynx. Therefore, the present study was designed to investigate the fine structure of taste buds located on the lamb epiglottis. MATERIALS Stained thick and semi-serial thin sections from taste buds located on the lamb epiglottis were examined with light and electron microscopy. RESULTS Based on morphological criteria, three types of cells could be identified in the taste bud: Type I, Type II, and basal cells. Both Type I and Type II cells extended into the apical taste pore, but there were differences between these two cell types with regard to nuclear profiles, electron density, and the relative density of ribosomes, apical mitochondria, and rough and smooth endoplasmic reticulum. Basal cells did not extend a process into the taste pore. Nerve processes were observed throughout the taste bud. Synapses were observed between both Type I and Type II cells and nerve fibers. These synapses exhibited membrane thickenings and accumulations of clear and dense-cored vesicles of varying proportions in the taste cell cytoplasm adjacent to membrane specializations. CONCLUSIONS The taste buds located on the lamb epiglottis share several structural similarities to taste buds located in the oral cavity and other regions of the pharynx and larynx of many mammalian species. The presence of synapses on both Type I and Type II cells of the lamb epiglottal taste bud suggests that both cell types are involved in laryngeal chemoreception.