Which type of muscle is characterized by a smooth appearance?

Smooth muscle is characterized by its lack of striations, giving it a smooth appearance. This type of muscle tissue is involuntary and is found in various structures throughout the body, such as the walls of hollow organs like the stomach, intestines, blood vessels, and the bladder. The smooth appearance is due to the uniform structure of individual muscle fibers, which do not have the banded appearance seen in skeletal and cardiac muscle tissues.

In contrast to smooth muscle, skeletal muscle fibers are long, cylindrical, and striated, indicating that they are under voluntary control and responsible for body movements. Cardiac muscle, found only in the heart, has a unique structure that includes striations and intercalated discs, enabling coordinated contraction but maintaining a distinct appearance from smooth muscle. Striated muscle refers broadly to muscles that have a striped or striated pattern, typically including skeletal and cardiac muscles, but does not apply to the smooth muscle category. Thus, the defining feature of smooth muscle is indeed its smooth, non-striated appearance.