Somatosensory innervation of healthy human oral tissues. Issue 11 (29th April 2021)

• Record Type: Journal Article
• Authors: Moayedi, Yalda; Michlig, Stéphanie; Park, Mark; Koch, Alia; Lumpkin, Ellen A.
• Is Part Of: Journal of comparative neurology. Volume 529:Issue 11(2021)
• Page Start: 3046
• Page End: 3061
• Publication Date: 2021-04-29
• Subjects: hard palate -- human -- mechanosensation -- tongue; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.25148
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: The oral somatosensory system relays essential information about mechanical stimuli to enable oral functions such as feeding and speech. The neurochemical and anatomical diversity of sensory neurons across oral cavity sites have not been systematically compared. To address this gap, we analyzed healthy human tongue and hard‐palate innervation. Biopsies were collected from 12 volunteers and underwent fluorescent immunohistochemistry (≥2 specimens per marker/structure). Afferents were analyzed for markers of neurons (βIII tubulin), myelinated afferents (neurofilament heavy, NFH), and Merkel cells and taste cells (keratin 20, K20). Hard‐palate innervation included Meissner corpuscles, glomerular endings, Merkel cell‐neurite complexes, and free nerve endings. The organization of these somatosensory endings is reminiscent of fingertips, suggesting that the hard palate is equipped with a rich repertoire of sensory neurons for pressure sensing and spatial localization of mechanical inputs, which are essential for speech production and feeding. Likewise, the tongue is innervated by afferents that impart it with exquisite acuity and detection of moving stimuli that support flavor construction and speech. Filiform papillae contained end bulbs of Krause, as well as endings that have not been previously reported, including subepithelial neuronal densities, and NFH+ neurons innervating basal epithelia. Fungiform papillae had Meissner corpuscles and densities of NFH+ intraepithelial neurons surrounding taste buds. The differing compositions of sensory endings within filiform and fungiform papillae suggest that these structures have distinct roles in mechanosensation. Collectively, this study has identified previously undescribed neuronal endings in human oral tissues and provides an anatomical framework for understanding oral mechanosensory functions. Abstract : Mechanosensory neurons in the human tongue and hard palate were identified using immunohistochemical methods. In fungiform taste papillae, Meissner‐like corpuscles were found within the lamina propria and putative mechanosensory neurons were identified that surround taste buds. In filiform non‐taste papillae, end bulbs of Krause were the predominant sensory ending. Novel sensory endings were also identified, including subepithelial neuronal densities and the endings of myelinated neurons that innervate the epithelium. In the hard‐palate mucosa, Meissner corpuscles and glomerular endings were identified in the lamina propria, and Merkel‐cell neurite complexes were identified in epithelia. This rich cadre of neuronal endings is poised to mediate mechanosensory control of feeding and speech.