By contracting, the muscle cells pull at their attached ends and cause body parts to move. The cells are elongated. By contracting, these muscles move the joints across which they lie. This causes movement, as when the joints of the legs are flexed and extended during walking. In addition, they generate heat when they contract, thus helping to maintain body temperature.
Cardiac muscle forms the mass of the heart.
By contracting it squeezes the blood out of the heart into the blood vessels. By contracting, it propels the contents along the tube it surrounds, as in the intestine, or regulates the amount of fluid flowing through it, as in the blood vessels.