Humans have over 650 muscles which differ in size according to the jobs they do. These muscles constitute 40% of body weight. The special function of muscle tissue is |contraction|. There are three kinds of muscle tissue: striated muscle, |smooth muscle|, and cardiac muscle. Most of the body's muscle consists of striated muscle which is the skeletal muscle. It is also called voluntary muscle because it can be consciously controlled via the central nervous system. |Smooth muscle| is the muscle of the internal organs and is called involuntary because it is not under voluntary control. Cardiac muscle is a special type of muscle found only in the |heart|. It consists of linked |fibers| that contract in unison producing the heartbeat.
