Vocal fold vibration of the canine larynx: Observation from an infraglottic view

The authors studied the vibratory action of the canine vocal fold from the tracheal side utilizing high-speed cinematography. Five excised canine larynges were used, and the lower surface of the vocal fold of three of them were marked with India ink as a tracer of a specific point on the vocal fold. A mucosal prominence, called the mucosal upheaval, appeared between the anterior commissure and the vocal process. Vibration was not seen below the mucosal upheaval. The mucosal wave started to move medially from just above the mucosal upheaval. The mucosal wave then became the free edge (lower lip) and collided with that of the other side at the midline. After collision, the lower lip moved upward to become the upper lip. At the same time, a part of the lower lip reflected laterally. The mucosal wave of the next cycle started from just above the mucosal upheaval during an opening phase. The mucosal upheaval vibrated with a low amplitude and with an earlier phase than the other portion of the vocal fold. The increase in tension of the vocal fold did not change the basic vibratory pattern of the mucosal upheaval, the mucosal wave, or the free edge. However, analysis of the mark before and after the increase in tension revealed that the mucosal upheaval occurred more medially or above when the vocal fold tension increased.