question: Myofibrils are long cylindrical structures that lie parallel to and run the entire length of what fibers?
distractor3: heart muscle fibers
distractor1: uplift muscle fibers
distractor2: luminous muscle fibers
correct_answer: skeletal muscle fibers
support: Skeletal Muscle Fiber Structure and Function Each skeletal muscle fiber is a skeletal muscle cell. Within each muscle fiber are myofibrils, long cylindrical structures that lie parallel to the muscle fiber. Myofibrils run the entire length of the muscle fiber. They attach to the plasma membrane, called the sarcolemma, at their ends, so that as myofibrils shorten, the entire muscle cell contracts (Figure 16.18).