Which type of muscle cell lacks the highlighted striations? The smooth muscle cell lacks visible striations. Unlike skeletal and cardiac muscle, smooth muscle does not display the regular light-and-dark bands produced by neatly organized contractile proteins. Its actin and myosin filaments are still present and highly effective, but they are arranged in a less regular pattern, so the tissue appears smooth when viewed through a light microscope. This feature is so characteristic that smooth muscle is also called non-striated muscle.
Why Smooth Muscle Cells Lack Striations
Striations are visible cross-bands that run across muscle fibers. In real terms, they form because the contractile proteins actin and myosin are arranged into repeating units called sarcomeres. Each sarcomere contains precisely positioned thick and thin filaments, creating the alternating dark A bands and lighter I bands seen in skeletal and cardiac muscle.
Smooth muscle contains both actin and myosin, but its filaments are not assembled into the same repeating sarcomere pattern. Instead, the proteins attach to structures called dense bodies. These dense bodies contain proteins similar to those found
