"part") is the basic unit of striated muscle tissue
. It is the repeating unit between two Z lines. Skeletal muscles
are composed of tubular muscle cells (myocytes
called muscle fibers
) which are formed in a process known as myogenesis
. Muscle fibers contain numerous tubular myofibrils
. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes.