Function of the interarytenoid(IA) muscle in phonation: in vivo laryngeal model

Thyroarytenoid(TA), lateral cricoarytenoid(LCA), and IA muscles are referred to as the adductors of the vocal fold. The TA is known to shorten the vocal folds and to adduct the membranous vocal fold, and the LCA adducts the inter-vocal process region and IA adducts the posterior commissure. Even though IA has an important role for the positioning of the vocal folds during respiration and phonation together with the action of the posterior cricoarytenoid muscle, little is known about the effect of IA on voice parameters during phonation. An in vivo canine model was used in five mongrel dogs to examine the role of the IA muscle in controlling phonation. In two out of five dogs, sound could not be elicited without stimulating the IA branches of the recurrent laryngeal nerves. When the IA was dynamically and statistically stimulated, subglottic pressure, vocal intensity and fundamental frequency were increased. However, open quotient was not changed markedly. These results suggest that the IA affects the voice parameters mainly by controlling subglottic pressure during phonation.