Interrelationship Between Intraepithelial Nerve Endings and Epithelial Cells in the Rat Epiglottis Revealed by Array Tomography With Scanning Electron Microscopy

Nerve endings in the laryngeal mucosa interact with epithelial cells to generate sensory discharges against various external stimuli. In the present study, we performed array tomography with scanning electron microscopy to examine the morphological interrelationship between intraepithelial nerve endings and epithelial cells in the rat epiglottis. In the epiglottic mucosa, thin nerve fibers/endings and ramified nerve endings were observed in the epithelial layer. Thin nerve fibers/endings had varicosities and terminal swellings, and ran in the shallow grooves of epithelial cells. The varicosities and terminal regions of the nerve fibers/endings were partially associated with epithelial cells, without any identifiable cell junctions or synaptic specializations. On the other hand, intraepithelial ramified nerve endings were detected in the stratified cuboidal epithelium at the base of the epiglottis. The ramified nerve ending consisted of a branched parent axon and large terminal parts that were approximately 3–6 µm in major axis length with irregular contours. The terminal parts of the ramified endings containing numerous mitochondria were closely attached to epithelial cells, as observed in the thin nerve fibers/endings. In conclusion, intraepithelial nerve endings in the epiglottis were in close contact with laryngeal epithelial cells and may be excited by mediators released from epithelial cells in response to various stimuli from the laryngeal lumen.