The picture explains the structure of muscle fibers in a sequence.

1. On the left, picture of a muscle with bundles of muscle fiber. The text box reads ‘A muscle consists of bundles of muscle fibers’.
2. Next is a picture of a muscle fiber. The text box reads ‘Each muscle fiber is a cell that contains many myofibrils’.
3. Following the muscle fiber is a picture of muscle fiber showing the sarcomere, actin and myosin. The text box reads ‘Each myofibril contains actin and myosin filaments’. The structural unit ‘sarcomere’ is labeled.
4. On the right, the structure of sarcomere is shown and various structural parts are labeled. The parts labeled are:

• Z line
• Actin
• Myosin

The text box reads ‘Two Z lines and the filaments between them make up a sarcomere’.