Classification of pharyngeal muscles based on innervations from glossopharyngeal and vagus nerves in human

The pharyngeal muscles are innervated by the glossopharyngeal and vagus nerves. However, their spatial interrelationships with the innervating branches have been unclear. This study examined the pharynx to elucidate their precise relationships for the anatomical evidence of the functional diagnosis.

The muscles and nerves were dissected under a binocular microscope in 44 sides of 22 cadavers fixed with 8% formalin.

The pharyngeal muscles overlapped each other, and the pharyngeal constrictors sometimes linked to adjacent muscles. The uppermost part of the superior constrictor arose from the soft palate, and sometimes contained the fibers attaching to the petrous part of the temporal bone. Anomalous bundles were frequently found between the superior and middle constrictors and the stylopharyngeus. The stylopharyngeus and the glossopharyngeal part of the superior constrictor were innervated by the glossopharyngeal nerve, which occasionally penetrated the stylopharyngeus. The pharyngeal plexus not only spread onto dorsolateral surface of the pharynx but also sent branches between the constrictors. The plexus supplied the superior constrictor and salpingo- and palatopharyngei from their dorsal surface and the middle and inferior constrictors from their ventral and dorsal surfaces. The inferior constrictor received additional innervations from the laryngeal nerves.

The innervations pattern suggests that the pharyngeal muscles comprise four groups: the first innervated by the glossopharyngeal nerve, the second and third by the pharyngeal plexus, and the fourth by the plexus and the laryngeal nerves. The stylopharyngeus descends between the second and third groups, and its penetration may cause the anomalous bundles between them.