FUNCTION OF THE INTERARYTENOID MUSCLE IN A CANINE LARYNGEAL MODEL

The interarytenoid (IA) muscle has rarely been studied in the living l arynx. In this work, the role of the IA muscle in phonation was studie d in three dogs by means of an in vivo phonation model. The isolated a ction of the IA muscle was studied by sectioning and stimulating its n erve branch. As IA activity increased, subglottic pressure increased s ignificantly until a plateau was reached. In the absence of superior l aryngeal nerve stimulation, the fundamental frequency rose with increa sing IA activity. In the presence of superior laryngeal nerve stimulat ion, however, no significant change in fundamental frequency was obser ved with increasing IA activity. Measurement of adductory force demons trated that the IA muscle adducts primarily the posterior vocal fold. In this canine model, phonation was not possible without IA stimulatio n, owing to a large posterior glottic chink.