n. a tissue whose cells have the ability to contract, producing movement or force (see illustration). Muscles possess mechanisms for converting energy derived from chemical reactions into mechanical energy. The major functions of muscles are to produce movements of the body, to maintain the position of the body against the force of gravity, to produce movements of structures inside the body, and to alter pressures or tensions of structures in the body. There are three types of muscle: striated muscle, attached to the skeleton; smooth muscle, which is found in such tissues as the stomach, gut, and blood vessels; and cardiac muscle, which forms the walls of the heart.
Muscle. A voluntary muscle in transverse section (left) and in longitudinal section at its junction with a ten-don (right).
Subjects: Medicine and health