They function as multi-cellular contractile units. The three types of muscle are skeletal, cardiac, and smooth . Skeletal muscle moves the skeleton and organs like the tongue and eye. It is under voluntary control. Its highly organized contractile proteins give a striated appearance.
Cardiac muscle generates the rhythmic contractions of the heart.
It is also striated. Smooth muscle does not have a striated appearance since its contractile apparatus is organized differently from that of the other muscle types. It lines viscera, the gastrointestinal tract, the uterus, and the bladder, and therefore is sometimes called visceral muscle. In addition it is found in the walls of blood vessels and the respiratory tract. The nuclei reside along the cell periphery.