Distribution of Taste Buds on the Epiglottis of the Rat and House Shrew, with Special Reference to Air and Food Pathways

Abstract

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.

Morphology of GNAT3‐immunoreactive chemosensory cells in the rat larynx

“…Shrestha et al. () demonstrated that only a few ‘taste buds’ were distributed near the edge of the oral surface of the epiglottis. In contrast, in the present study, chemosensory cell clusters were concentrated at the anterior border of the larynx, including the edge of the epiglottis, aryepiglottic fold, and mucosa covering arytenoid cartilage.…”

“…The mucosa overlying epiglottic cartilage may also be a receptive field for chemical stimuli. Chemosensory cell clusters have been reported as laryngeal taste buds in various species (Travers & Nicklas, 1990;Sweazey et al 1994;Shrestha et al 1995;Nishijima & Atoji, 2004;Sbarbati et al 2004b). Chemosensory clusters are mainly distributed in the laryngeal surface of the epiglottis and aryepiglottic fold in the rat larynx (Nishijima & Atoji, 2004;Sbarbati et al 2004b).…”

“…Chemosensory clusters are mainly distributed in the laryngeal surface of the epiglottis and aryepiglottic fold in the rat larynx (Nishijima & Atoji, 2004;Sbarbati et al 2004b). Shrestha et al (1995) demonstrated that only a few 'taste buds' were distributed near the edge of the oral surface of the epiglottis. In contrast, in the present study, chemosensory cell clusters were concentrated at the anterior border of the larynx, including the edge of the epiglottis, aryepiglottic fold, and mucosa covering arytenoid cartilage.…”

Quantitative study of ageing epiglottal taste buds in humans

“…Sherestha et al. 6 suggested that because the number of epiglottal taste buds varies by species, their presence may correlate with feeding habits. It could be suggested that in elderly people, the decrease of epiglottal taste bud density on the laryngeal surface may have an effect on the reflex response during swallowing.…”

“…The hamster epiglottis is said to contain about 10% of the total number of taste buds 4 , whilst the human epiglottis is estimated to contain up to 25% of the total. Although taste buds are sensory organs, those on the epiglottis may have an important role in protecting the upper airway by functioning as chemical receptors 5,6 However, age‐related changes on the number and distribution of epiglottal taste buds have not been fully investigated and whether they continue to play a functional role in protecting the upper airway. Previous studies have documented age‐related changes in the number of taste buds in the epiglottis of the rat 7 and sheep 8 .…”