Distribution of taste buds on the epiglottis of the rat and house shrew, with special reference to air and food pathways.

We investigated the positioning of the epiglottis in the pharyngo-laryngeal region and the distribution of taste buds on the epiglottis in the rat and house shrew, animals which have different feeding habits. In the fixed samples of both species, when the mouth was closed or slightly opened, the epiglottis was found to protrude into the nasopharyngeal hiatus above the soft palate. But it retracted from its position when the mouth was widely opened. In omnivorous rats (n = 6), the mean number (mean density +/- s.d.) of taste buds was 52 (12.6 +/- 2.2/mm2) on the laryngeal surface but only 4 (1.3 +/- 1.0/mm2) on the oral surface. The three-dimensional view was reconstructed from serial sections. The taste buds were distributed most densely close to the caudal base and became fewer toward the more rostral tip. In insectivorous house shrews (n = 2), 4 taste buds on average were found only on the laryngeal surface of the epiglottis. Epiglottal taste buds may work as chemosensory detectors to initiate the reflex reaction to protect the airway from oral substances during swallowing and drinking.