Abstract
In order to clarify the functional subunits in a single laryngeal muscle, electrophysiological and histochemical studies were performed. The thyroarytenoid muscle was divided into the rostral compartment and the caudal compartment. The posterior cricoarytenoid muscle was divided into the lateral and the medial compartment.
EMGs were recorded during normal respiration and mechanically-evoked cough from rostral (r-TA) and caudal (c-TA) compartment of thyroarytenoid muscle along with lateral (l-PCA) and medial (m-PCA) compartment of posterior cricoarytenoid muscle. Histochemical detection of myosin ATPase and EMGs revealed that the type 2B fiber was most abundant in r-TA and gradually decreased in the order of c-TA, l-PCA and m-PCA.
During cough, these four compartments of muscles equally exhibited bursting discharges. L-PCA activity during cough exhibited a ninefold increase over that during respiration, while m-PCA exhibited a threefold increase. These data suggest that the intrinsic laryngeal muscle consists of different compartment with distinctive motions. Hence the intrinsic laryngeal muscles should be considered as a complex of some functional subunits.
