What is a key characteristic of smooth muscle?

Smooth muscle is characterized primarily by its fusiform shape, which means that the muscle fibers are tapered at both ends and wider in the middle. This shape allows smooth muscle cells to contract in a coordinated and efficient manner, enabling them to facilitate various involuntary movements in the body, such as the contraction of blood vessels and the movement of food through the digestive tract.

In addition to its fusiform shape, smooth muscle fibers are not striated, which distinguishes them from skeletal and cardiac muscles that have a striated appearance due to the regular arrangement of actin and myosin filaments. Smooth muscle is also typically uninucleated rather than multinucleated, as seen in skeletal muscle, and it operates under involuntary control, meaning its activity is regulated by the autonomic nervous system rather than conscious effort. These characteristics are crucial for the diverse functions smooth muscle performs throughout the body.