The A and I bands repeat along the length of the muscle fibers to create the striations visible under the light microscope. About Sarcomeres Sarcomeres repeat along skeletal and cardiac fibers. Components between adjacent Z-lines comprise the sarcomere. Sarcomeres are considered the functional units of striated muscles. A Bands are areas where some overlap occurs and coincide with the length of myosin myofilaments.
Striations are a key attribute to identify skeletal and cardiac muscle types.
Although striations are usually visible in most sections of these muscle types, it can sometimes take a little adjustment of the microscope lighting to see them clearly. Also, striations are only visible in longitudinal views of myofibers so it is essential some part of the muscle section being evaluated includes this type of cut. Remember, striations across cells indicate you are viewing cardiac or skeletal muscle. Differentiation of these two types involves other structural features. Skeletal Muscle Skeletal muscle is the most abundant muscle type in the body.