Which statement best describes muscle fibers?

• A. They are multinucleated muscle cells surrounded by endomysium
• B. They are single-nucleus cells without surrounding tissue
• C. They are unstriated fibers lining hollow organs
• D. They are noncontractile extracellular components

Answer: (A)

Muscle fibers in skeletal muscle are long, cylindrical cells that contain many nuclei because they form by the fusion of multiple myoblasts. Each fiber is wrapped in a delicate connective tissue layer called the endomysium. This combination—multinucleated cells with an endomysial sheath—reflects how skeletal muscle is organized to receive nerve signals and blood supply and to transmit force efficiently to the tendon. The alternative descriptions describe other tissue types (such as smooth muscle, which is unstriated and usually single-nucleated or lacking an endomysial arrangement) and do not capture the defining structure of skeletal muscle fibers.