The layer that groups muscle fibers into bundles is called which?

• A. Endomysium
• B. Epimysium
• C. Fascia
• D. Perimysium

Answer: (D)

Muscle tissue is organized in layers of connective tissue that progressively wrap larger units. The layer that groups several muscle fibers into a bundle is perimysium, which surrounds each fascicle—the bundle of fibers inside a muscle. The perimysium sits between the inner endomysium, which wraps individual fibers, and the outer epimysium, which encases the whole muscle. It also contains blood vessels and nerves that service the fibers within the fascicle, helping coordinate contraction and supply. The epimysium covers the entire muscle, while fascia refers to broader connective tissue that surrounds muscles or muscle groups. So, perimysium is the structure specifically responsible for organizing muscle fibers into bundles.