EM Skeletal muscle Longitudinal Section
At the fine structural level it is easier to see the A and I bands. I bands are divided by Z lines. A sarcomere runs from one Z line to the next. A series of sarcomeres that run the length of the muscle fiber is called a myofibril. The A band is divided by the H band which in turn is divided by the M line. The H band is the region where only myosin exists. The I band is the region where only actin exists.