Tracheal view of vocal fold vibration in excised canine larynxes

The mucosal upheaval where the mucosal wave starts and propagates upward appears on the lower surface of the vocal fold during vibration. We investigated the location of the mucosal upheaval in response to variations in vocal fold tension and mean air flow rate. Twelve excised canine larynxes were used in the experiment. The lower surfaces of the vocal folds were marked with india ink. After cinematography was performed, a small cut wound was made at the mark. This wound served to relate cinematographic findings with the histologically observed position of the mark. The larynx was then fixed, sectioned in the frontal plane, and stained for histologic examination. Horizontal movements of the free edge, mucosal wave, mucosal upheaval, and marks were analyzed. Under a fixed vocal fold tension, the mucosal upheaval appeared more laterally to a limited extent as mean air flow rate increased, but its location on the vocal fold mucosa did not change from its position before the increase of mean air flow rate. The mucosal upheaval appeared more medially when vocal fold tension increased. The position of the mucosal upheaval actually changed medially compared with its original position before the tension increase. Histologic examination indicated that the mucosal upheaval arose on the lower surface of the vocal fold between the free edge and the area where the muscular layer comes in close proximity to the epithelial layer.