Smooth muscle is a type of involuntary muscle found in various organs and structures within the body. It is called smooth muscle because it does not have striations (the appearance of bands or lines) under a microscope, unlike skeletal or cardiac muscles. Smooth muscles are responsible for performing functions such as moving food through the digestive system, regulating blood flow by constricting and dilating blood vessels, controlling the size of the pupil in the eye, and more. These muscle contractions are generally slower and more sustained than those produced by skeletal or cardiac muscles, allowing for better control over bodily functions.