Final answer:
Muscle myofibrils contain myosin and actin myofilaments, extend from the sarcolemma across the muscle fiber, and contribute to the striated appearance of skeletal muscle.
Step-by-step explanation:
The feature(s) of muscle myofibrils include:
- Contain myosin and actin myofilaments: Myofibrils are made of repeating units called sarcomeres, which contain thick (myosin) and thin (actin) filaments.
- Extend from the sarcolemma to the T-tubule: Myofibrils attach at the sarcolemma and span the entire length of the muscle cell.
- Appear striated: The organized arrangement of actin and myosin myofilaments creates a banding pattern that appears as striations.
Other features, such as holding muscle cells together or being found in the sarcolemma, are not characteristics of myofibrils.