Sensory Innervation of the Human Soft Palate

Abstract

The human soft palate plays an important role in respiration, swallowing, and speech. These motor activities depend on reflexes mediated by sensory nerve endings. To date, the details of human sensory innervation to the soft palate have not been demonstrated. In this study, eight adult human whole-mount (soft palate-tongue-pharynx-larynx-upper esophagus) specimens were obtained from autopsy. Each specimen was bisected in the midline, forming two equal and symmetrical halves. Eight hemi-specimens were processed with Sihler's stain, a whole-mount nerve staining technique. The remaining eight hemi-soft palates were used for immunohistochemical study. The soft palatal mucosa was dissected from the oral and nasal sides and prepared for neurofilament staining. Our results showed that the sensory nerve fibers formed a dense nerve plexus in the lamina propria of the soft palatal mucosa. There was a significant difference in the innervation density between both sides. Specifically, the oral side had higher density of sensory nerve fibers than the nasal side of the soft palate. The mean number and percent area of the sensory nerve fibers in the mucosa of the nasal side was 78% and 72% of those in the mucosa of the oral side, respectively (P < 0.0001). The data presented here could be helpful for further investigating the morphological and quantitative alterations in the sensory nerves in certain upper airway disorders involving the soft palate such as obstructive sleep apnea (OSA) and for designing effective therapeutic strategies to treat OSA. Anat Rec, 301:1861-1870, 2018. © 2018 Wiley Periodicals, Inc.

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“…We found the sensory nerves were significantly decreased in CIH-induced rat. Sensory inputs from the upper airway play an important role in initiation of various physiological reflexes and in feedback control of motor activities [27]. Clinical testing of the soft palate and pharyngeal mucosa in OSA patients by cold sensory testing showed upper airway sensory impairment [28].…”

Upregulation of HMGB1 promotes vascular dysfunction in the soft palate of patients with obstructive sleep apnea via the TLR4/NF‐κB/VEGF pathway

“…The human soft palate is one of key structures involved in repetitive obstruction and breathing interference during sleep [ 3 ]. OSA patients with IH mainly result from a pathological progression followed by the collapse of the soft palate.…”

“…This disorder is characterized by the collapse of the soft palate in the upper airway, resulting in chronic intermittent hypoxia (IH) during sleep [ 2 ]. Several studies have demonstrated that the collapse of the soft palate might result from pathophysiological changes in inflammatory infiltration, an increase in mucosa thickness and abnormal afferent nerve endings [ 3 ]. It was also reported that soft palates from OSA patients were characterized by mucous gland hypertrophy, focal atrophy of muscle fibers and extensive edema of the lamina propria [ 4 ].…”