The muscular system refers to the series of muscles in the entire body that allows movement of the skeleton, maintains posture and produces heat through cell metabolism, according to Healthline. The muscles comprising the muscular system not only move the bones, but they also make the heart beat.
The muscular system is composed of three types of muscle tissues: skeletal muscle, smooth muscle and cardiac muscle. The skeletal muscles are responsible for body movement and roughly 40 percent of a person's body weight. Smooth muscles refer to the involuntary muscles that make up organ walls, and the cardiac muscles are the involuntary muscles responsible for heart contractions.