Which tissue is not composed of striated muscle fibers?

• A. Smooth muscle
• B. Nervous tissue
• C. Cardiac muscle
• D. Skeletal muscle

Answer: (A)

Striated versus non-striated muscle tissue is what this item asks you to distinguish. Striated muscle fibers have a banded appearance under a microscope because their fibers are organized into repeating sarcomeres. This pattern is found in skeletal muscle, which is under voluntary control, and in cardiac muscle, the heart muscle, which is also striated but contracts involuntarily. Smooth muscle lacks those bands; its spindle-shaped cells form non-striated tissue that contracts more slowly and is responsible for moving contents through hollow organs and vessels. Nervous tissue isn’t muscle at all; it’s made of neurons and supporting cells and handles signaling rather than contraction. So the tissue that is not composed of striated muscle fibers is smooth muscle.