What is the cause of the striated appearance of skeletal and cardiac muscle?

• A. The uniform distribution of mitochondria
• B. The presence of intercalated discs
• C. The presence of dense bodies
• D. The arrangement of actin and myosin filaments in sarcomeres

Answer: (D)

Verified step by step guidance

1. Begin by understanding the structure of muscle fibers, specifically skeletal and cardiac muscle. These muscles are composed of repeating units called sarcomeres.
2. Sarcomeres are the basic functional units of muscle fibers and are responsible for muscle contraction. They contain organized arrangements of actin (thin filaments) and myosin (thick filaments).
3. The striated appearance of these muscles is due to the specific arrangement of actin and myosin within the sarcomeres. This arrangement creates alternating light and dark bands visible under a microscope.
4. The dark bands, known as A bands, contain the entire length of the myosin filaments and some overlapping actin filaments. The light bands, known as I bands, contain only actin filaments.
5. This pattern of alternating bands is what gives skeletal and cardiac muscle their characteristic striated appearance, distinguishing them from smooth muscle, which lacks this organized banding pattern.