Muscle structure, skeletal muscle, muscle bundle and fiber. The muscle is attached to the bone by the tendon. It is covered by the deep fascia. Several muscle bundles make up muscle. A first membrane called epimysium covers these bundles. But each bundle is also covered by a membrane called the perimysium. They are also made up of a number of muscle fibers covered with endomysium. Myofibrins are the last units of muscle structure. They are not isolated in this drawing. But they are represented by the pinkish beige dots on the section of the muscle fiber.