A complex muscle fiber network in the cricothyroid muscle: a scanning electron microscopic study.

OBJECTIVES: To examine the three-dimensional ultrastructure of cricothyroid (CT) muscle fibers to elucidate their morphologic characteristics with regard to the specific functions of the muscle. STUDY DESIGN: An anatomic animal study. METHODS: The CT muscles of five adult rats were processed using the HCl-hydrolysis method to remove the peri- and intramuscular connective tissue components. The fine muscle fiber arrangements were observed by scanning electron microscopy. RESULTS: Complex muscle fiber interconnections (myomyous junctions) were identified in the muscles. Myomyous junctions were characterized by the connection of many villous processes that were 1 to 2 mum in diameter and 2 to 4 mum in length with a serrated appearance at the ends of a lateral branch or a bifurcating trunk of the muscle fibers. CONCLUSIONS: Myomyous junctions form a complex muscle fiber network, which is thought to synchronize the activity of the CT muscle fibers. This is the first three-dimensional demonstration of the muscle fiber network in the CT muscle; this network may play a major role in the functional specificity of the CT muscle.