束肌纤维 一条肌纤维 条肌原纤维 带 A带—1带一1A带—1{带 中, lH带 一个肌节M线 线 个肌节 Sarcomere: a segment of myofibril extending from one z line to next z line. which is composed of 1/2 i band, a band and 1/2 I band which is the smallest structural and functional unit of skeletal muscle fiber.* Sarcomere: a segment of myofibril extending from one Z line to next Z line, which is composed of 1/2 I band, A band and 1/2 I band ,which is the smallest structural and functional unit of skeletal muscle fiber