The three-dimensional arrangement of myofibril and mitochondria in five intrinsic laryngeal muscles, i. e. the cricothyroid, thyreoarytenoid, lateral cricoarytenoid, posterior cricoarytenoid and arytenoid muscles, were investigated by means of field emission scanning electron microscopy. The findings were as follows:
1. The basic structure of the myofibril, sarcoplasmic reticulum, transverse tubules and sarcolemma of the intrinsic laryngeal muscle were essentially the same as that of other skeletal muscles of mammals.
2. There are no significant differences in the structures of the five intrinsic laryngeal muscles.
3. Three types of mitochondria were observed underneath the sarcolemma: (1) Many mitochondria of round or rod-like shape,(2) A few elongated mitochondria, running parallel to the myofibrils,(3) Mitochondria with complex shapes e. g. spiral, tree-like and horsebean. The former two shapes were found frequently in the lateral portion of the thyreoarytenoid muscle and in the other four muscles, while the complex shape was found in the medial portion of the thyreoarytenoid muscle.
4. Three types of mitochondria were found between myofibrils: (1) Mitochondria of round or rod-like shape,(2) Elongated mitochondria, running parallel to the myofibrils, and (3) Mitochondira running perpendicular to myofibrils with branches of different shapes. The former two were found frequently in the lateral portion of the thyreoarytenoid muscle and in the other four muscles, while the latter was found in the medial portion of the thyreoarytenoid muscle.
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