The external laryngeal nerve is a branch of the vagus nerve. It forms from the superior laryngeal nerve as it divides at about the level of the hyoid bone. It passes inferiorly within the carotid sheath, posterior to the common carotid artery, and then anteriomedially next to the superior thyroid artery.
The external laryngeal nerve ramifies on the surface of the inferior constrictor muscles before piercing them. It supplies special visceral motor fibres to the cricothryroid muscle. Also, it may supply a few motor fibres to the cricopharyngeus part of the inferior constrictors as it passes through. Both sets of nerve fibres originate from nuclei within the nucleus ambiguus of the medulla.