Fig. 2. The superior and middle constrictors of the pharynx and the thyropharyngeus muscles lie together from the pharyngeal ligament down to the level of the vocal cords. (Bottom ) The posterior wall of the esophagus is only the single sheet of the thyropharyngeus (the dehiscence of Killian) that allows herniation of the esophageal diverticulum, and is always above the cricoid arch.