Superior Laryngeal Nerve

Abstract

Although the number of nerve fibers constituting the superior laryngeal nerve varies among species, the component ratio of myelinated to unmyelinated fibers is consistently about 1:1. Using a fluorescent histochemical technique and nerve tracers, we have demonstrated the presence of the projection pathway of the autonomic nerve via internal and external branches to the larynx. Although there is controversy regarding the presence/absence of motor nerve fibers in the internal branch, we have identified motor nerve cells of the facial nerve nucleus extending fibers to the internal branch and revealed motor nerve fibers to be present in the internal branch. We have also demonstrated that the internal branch contains calcitonin gene-related peptide, substance P, and leu-enkephalin.