Cardiac muscle is a type of involuntary striated muscle found in the walls of the heart, specifically the myocardium. Cardiac muscle cells are known as cardiac myocytes (or cardiomyocytes). Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle. The cells that comprise cardiac muscle are sometimes seen as intermediate between these two other types in terms of appearance, structure, metabolism, excitation-coupling and mechanism of contraction. Cardiac muscle shares similarities with skeletal muscle with regard to its striated appearance and contraction, with both differing significantly from smooth muscle cells.

Coordinated contraction of cardiac muscle cells in the heart propel blood from the atria and ventricles to the blood vessels of the circulatory system. Cardiac muscle cells, like all tissues in the body, rely on an ample blood supply to deliver oxygen and nutrients and to remove waste products such as carbon dioxide. The coronary arteries fulfill this function.

For more information about Cardiac muscle, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.