Morphological Observation on Silver-impregnated Nerve Endings in Human Interarytenoid Muscle

Light microscopic study of nerve endings in the human interarytenoid muscle was carried out by using the Baker's silver impregnated materials. In addition to the ordinary motor nerve endings, there were three types of nerve endings surrounding the muscle fibers in an annular or helical manner. The first type of the ending was composed of a thick myelinated fiber which tightly encircled and wrapped the muscle fibers. Branches from the myelinated fibers sporadically formed end buttons and loops. This type was determind as the spiral nerve ending. The second type of the ending had several muscle fibers possessing both the spiral nerve ending and motor nerve ending. This type of the ending was considered to be the muscle spindle. The third type of the ending was composed of both the spiral ending and motor nerve ending, which were thought to be either the nerve ending of the mixed type or the motor ending of the diffuse type. These were the additional findings to our first report that revealed the presence of muscle spindles in the intrinsic laryngeal muscles. A similar system has been found only in the outer ocular muscles.