What best describes smooth muscles?

Smooth muscles are characterized as non-striated and involuntary. This means that they do not have the striped appearance seen in striated muscles such as skeletal and cardiac muscle, which results from the regular arrangement of muscle fibers. Instead, smooth muscle fibers are more uniform and lack these visible striations, appearing more like a solid sheet rather than distinct fibers.

The involuntary nature of smooth muscle means that it operates without conscious control. These muscles are primarily found in the walls of hollow organs such as the intestines, blood vessels, and the bladder. They are responsible for various automatic processes such as peristalsis in the digestive system and regulating blood flow through vasoconstriction and vasodilation in blood vessels.

This understanding helps distinguish smooth muscles from skeletal muscles, which are striated and under voluntary control, and cardiac muscles, which though striated, are also involuntary. Therefore, recognizing the unique characteristics of smooth muscle is essential in studying the muscular system and its functions within the human body.