Smooth Muscle

Smooth muscle is distributed widely throughout the body and is more variable in function than the skeletal muscle and cardiac muscle. Smooth muscle cells are smaller than skeletal muscle cells. They are spindle-shaped, with a single nucleus located in the middle of the cell. Compared with skeletal muscle, there are fewer actin and myosin myofilaments. Although the myofilaments approximate a longitudinal, or spiral, orientation within the smooth muscle cell, they are not organized into sarcomeres. Consequently, smooth muscle does not have a striated appearance.