Morphological Study of the Laryngeal Muscles in Man: Insertions and Courses of the Muscle Fibres, Motor End-Plates and Proprioceptors

Abstract

Koelle and Friedenwald's test for acetylcholinesterase has been used in a study on the following laryngeal muscles in man: vocalis, cricothyroid, lateral crico-arytenoid and posterior crico-arytenoid. Serial sections were made with the freezing microtome and a number of muscles were submitted to microdissection. “Multi-motor end-plate” fibres were found in all four muscles studied (70 to 80 per cent in the vocalis muscle, about 50 per cent in the cricothyroid and lateral crico-arytenoid muscles and about 5 per cent in the posterior crico-arytenoid muscle). None of the fibres of the vocalis muscle was found to be inserted into the vocal ligament. Only in the vocalis muscle was it possible to demonstrate typical muscle spindles, whereas in all four muscles studied “spiral nerve endings” were observed.