Vocal Fold Vibration of the Canine Larynx : Observation from the Tracheal Side

The authors investigated vibratory mode of the vocal fold seen from the tracheal side utilizing a high speed cinematography. Twelve excised canine larynges were used in the experiment. Several marks were made with Indian ink on the lower surface of the vocal folds. After taking cinematography, the larynges were fixed, sectioned in a frontal plane and stained for histologic examination. Movements of the free edge, lower lip, mucosal upheaval and marks were analyzed. The mucosal upheaval appeared on the lower surface of the vocal fold during vibration. Mucosal waves started from the mucosal upheaval, which itself vibrated with a small amplitude. The mucosal upheaval was placed more laterally when the air flow rate was increased. But the mucosal upheaval occured at the same location on the mucosa as that before the increase of air flow rate. This was because the increased subglottic pressure displaced the vocal fold laterally and upward. When vocal fold tension was increased, the mucosal upheaval was situated more medially. The location of the mucosal upheaval on the mucosa moved medially compared to 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 was close to the epithelial layer.