Anatomical analysis of the muscle layers of the soft palate in velopharyngeal closure: A cadaveric study

Background: In general, the levator veli palatini is essential for velopharyngeal closure as it elevates the velum. However, reconstructing the levator veli palatini alone does not fully restore velopharyngeal closure, suggesting that surrounding muscles-particularly the palatopharyngeus and superior constrictor-are also essential. We aimed to clarify the spatial relationships between the muscle bundles of the soft palate and pharynx macroscopically and histologically, particularly the palatopharyngeus, superior constrictor, and levator veli palatini. Methods: We examined 15 heads from adult Japanese cadavers-12 macroscopically and three histologically. Results: We observed superior constrictor attaching to the most lateral part of the soft palate and three consistently identifiable fiber groups, classified according to their origin on the superior or inferior surface of the soft palate and their relationship to the levator veli palatini. The superolateral part of the palatopharyngeus originated inferior to the levator veli palatini and ran obliquely and transversely on the pharyngeal wall. The superomedial part of the palatopharyngeus originated from the superior surface of levator veli palatini, ran orthogonally to levator veli palatini, and comprised the palatopharyngeal arch. The inferior part of the palatopharyngeus originated from the inferior surface of the palatine aponeurosis and comprised the palatopharyngeal arch. Moreover, the inferior part of the palatopharyngeus was attached to the base of the epiglottis and thyroid cartilage. Conclusions: The multidirectional bundles of the palatopharyngeus, superior constrictor, and levator veli palatini within the soft palate are closely related anatomically and play important roles in velopharyngeal closure.