Abstract
The main purpose of this investigation is to elucidate the functions of the intrinsic and extrinsic larygeal muscles in deglutition, especially their participation in elevation of the larynx. In preliminary experiment, using mongrel dogs, adequate frequencies for reflex deglutition elicited by electrical stimulations of the internal branch of the superior laryngeal nerve were determined (20-30 Hz). In addition, relation between respiration and deglutition was examined.
Two types of observation were made for the main purpose:1) simultaneous recordings of electromyogram of selected fifteen muscles, i. e. the cricothyroid, thyroarytenoid, arytenoid, stylohyoid, mylohyoid, geniohyoid, thyrohyoid, sternohyoid, sternothyroid, hyopharyngeal, thyropharyngeal, cricopharyngeal muscles, and laryngeal movements during deglutition elicited by the water pouring in pharynx or repeated electrical stimulations of the internal branch of the superior laryngeal nerve, were performed with a polygraph unit, and 2) measurement of elevation of the larynx and the hyoid bone during deglutition before and after deletion of the function of some selected muscles was also performed.
On the basis of the results, the following conclusions appear justified.
1) Activities of the intrinsic and extrinsic laryngeal muscles are highly consistent in each deglutition, and the larynx is closed and elevated by their coordinatory function.The pre-programed command of the centrum on each muscle is not influenced by deletion of some selected muscles.
2) The geniohyoid and thyrohyoid muscles play the most important role in elevating the larynx during deglutition.
3) The mylohyoid, stylohyoid and tongue muscles participate in elevation of the larynx to some extents.
