The Fine Structure of Smooth Muscle in Bipalium Kewense Moseley, Its Possible Relation to Evolution of Skeletal Muscle

抄録

The fine structure of the smooth muscles in a land Turbellarian, Bipalium Kewense, has been studied. These muscles are composed of three types myofilaments. Besides the thick and the thin filaments, there is a third type of intermediate filament which forms networks to connect between the dense bodies. The nucleus, mitochondria, sarcoplasmic reticulum are mainly at the periphery of the muscle.
Two types of glycogen granules with different sizes have been encountered; both scattered among myofilaments as well as close to mitochondria. One type exhibits a round granular appearance while the other is usually of a rosette form. Dense bodies closely associated with the sarcoplasmic reticulum, which are vesicular or tubular in appearance, are also encountered. The possible evolutionary aspects of skeletal muscle are considered.