In skeletal muscle:

• A. thick filaments which are made up of myosin and tropomyosin are lined up to form A bands
• B. the dark A band has a light H band in its centre which in turn has an M line in its middle
• C. think filaments are made up of actin, tropomyosin and troponin and form the H band
• D. Z lines are connected to the thick filaments
• E. during contraction, the width of the A band reduces