FUNCTION OF THE THYROARYTENOID MUSCLE IN A CANINE LARYNGEAL MODEL

Fundamental frequency is controlled by contraction of the thyroaryteno id (TA) and cricothyroid (CT) muscles. While activity of the CT muscle is known to tense and thin the vocal folds, little is known about the effect of the TA muscle on vocal fold vibration. An in vivo canine la ryngeal model was used to examine the role of the TA muscle in control ling phonation. Isolated TA muscle activation was obtained by stimulat ing sectioned terminal TA branches through small thyroid cartilage win dows. Subglottic pressure measures, electroglottographic and photoglot tographic signals, and acoustic signals were obtained in 5 mongrel dog s during dynamic and static variations in TA muscle activity. Results indicated that TA muscle activation is a major determinant in sudden s hifts from high-frequency to modal phonation. Subglottic pressure incr eased and open quotient decreased gradually with increasing TA activat ion.