Morphology of the Nerve Terminals of Laryngeal Muscles in the Japanese Monkey (Macaca fuscata)

Abstract

Summary: Laryngeal muscles, namely, the cricothyroid (CT), lateral crico-arytenoid (LCA), thyrio-arytenoid (TA), posterior crio-arytenoid (PCA), interarytenoid (IA) muscles, of Japanese monkeys (body weight, 4.4-8.3 kg; 3-10 years old, male) were examined histologically and by light and scanning electron microscopy. The diameter of muscle fibres with nerve terminals in the CT of the Japanese monkey was larger than that of other laryngeal muscles. However, the areas of nerve terminals varied among laryngeal muscles. The mean diameters of nerve terminals of the CT and PCA were large and basically resembled those of other laryngeal muscles. They contribute mainly to maintenance of phonation which the adductor muscles contribute mainly to postural adjustments of the cartilage. The differences in features of nerve terminals of each muscle suggest the CT and PCA may contribute mainly to the frequency or pitch of voice and intensity of the voice during vocalization and to respiration.The laryngeal muscles of mammals have various enzymatic profiles (e.g