Anatomy And Physiology – Muscular System Practice Test

At the core of this question is how skeletal muscle is built from large to small units. A muscle is made up of bundles called fascicles, and each fascicle contains many muscle fibers (also called muscle cells). Inside each muscle fiber are long, threadlike structures called myofibrils, and the sarcomere sits within a myofibril as its basic contractile unit. So the correct sequence is: muscle → fascicle → muscle fiber (myofiber) → myofibril → sarcomere. Mitochondria are energy-producing organelles scattered within the muscle fibers; they’re important for function, but they aren’t a distinct structural level in the hierarchy between fibers, myofibrils, and sarcomeres. The term fibril isn’t the standard level in this context, and placing the sarcomere after a structure like a mitochondrion would misplace the sarcomere’s position inside the myofibril. This is why the described order aligns with the actual organization from whole muscle down to the contractile unit.