Morphology of the nerve endings in laryngeal mucosa of the horse.
Authors: Yamamoto Y, Atoji Y, Hobo S, Yoshihara T, Suzuki Y
Journal: Equine veterinary journal
Summary
# Editorial Summary: Nerve Endings in the Equine Larynx Understanding laryngeal sensation is fundamental to managing disorders affecting the horse's upper airway, yet the sensory architecture of this region remained poorly characterised until this detailed morphological study. Yamamoto and colleagues used immunohistochemistry and electron microscopy to map sensory structures throughout the equine laryngeal mucosa, identifying three distinct types: glomerular endings (concentrated in the epiglottis and arytenoid regions), taste buds (distributed across the epiglottis and aryepiglottic fold), and intraepithelial free nerve endings rich in neuropeptides including substance P and calcitonin gene-related peptide. Notably, sensory innervation density varied markedly by location—the corniculate process of the arytenoid region showed the highest concentration of free nerve endings (30.6 CGRP-positive and 10.0 substance P-positive endings per mm epithelial length), whilst the vocal fold mucosa was sparsely innervated (1.1 and 0.8 per mm respectively). These regional differences in sensory receptor distribution suggest the larynx employs location-specific mechanisms for detecting threats, which has implications for understanding inflammatory conditions, dysfunction of swallowing and respiration, and how laryngeal trauma or surgical intervention might affect protective reflexes in the resting and exercising horse.
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Practical Takeaways
- •Understanding the variable distribution of sensory nerve endings across laryngeal regions may help explain why certain areas (arytenoid, epiglottis) are more sensitive to irritation and contribute to different types of laryngeal dysfunction
- •The high concentration of neuropeptide-containing nerve endings in the arytenoid region suggests this area plays a critical role in laryngeal protection and reflex responses
- •Knowledge of these sensory mechanisms may inform clinical assessment of laryngeal disorders and help differentiate between conditions affecting different laryngeal regions
Key Findings
- •Glomerular nerve endings are distributed mainly in epiglottic mucosa and arytenoid region, with some terminals directly contacting epithelial cells
- •Taste buds are present in epiglottis and aryepiglottic fold epithelium, supplied by terminal branching of thick nerve fibres
- •Intraepithelial free nerve endings immunoreactive for CGRP and substance P show highest density in corniculate process (30.6±12.0 CGRP and 10.0±4.9 SP per mm) and lowest in vocal cord mucosa (1.1±0.9 CGRP and 0.8±0.7 SP per mm)
- •Laryngeal mucosa demonstrates morphology- and location-dependent sensory mechanisms suggesting differential responses to various stimuli