Which structure contains the repeating units called sarcomeres within the skeletal muscle fiber?

Which structure contains the repeating units called sarcomeres within the skeletal muscle fiber?

• A. Nucleus
• B. Myofibril
• C. Endomysium
• D. Perimysium

Answer: (B)

Sarcomeres—the repeating contractile units of skeletal muscle—are organized along a myofibril inside each muscle fiber. A skeletal muscle fiber contains many myofibrils running along its length, and each myofibril is made up of a chain of sarcomeres bounded by Z-discs. This arrangement lets the filaments slide past each other during contraction, shortening the sarcomeres and thus the whole fiber. The nucleus is the cell’s genetic control center, while endomysium and perimysium are connective tissue layers around fibers and fascicles, not structures that contain sarcomeres.

Sarcomeres—the repeating contractile units of skeletal muscle—are organized along a myofibril inside each muscle fiber. A skeletal muscle fiber contains many myofibrils running along its length, and each myofibril is made up of a chain of sarcomeres bounded by Z-discs. This arrangement lets the filaments slide past each other during contraction, shortening the sarcomeres and thus the whole fiber. The nucleus is the cell’s genetic control center, while endomysium and perimysium are connective tissue layers around fibers and fascicles, not structures that contain sarcomeres.