Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle. The cells that comprise cardiac muscle are called cardiomyocytes and are sometimes seen as an intermediate between other types of muscle 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. In addition, cardiac muscle cells, like skeletal muscle cells, are multinuclear whereas smooth muscle cells are mononuclear.
Coordinated contraction of cardiac muscle cells in the heart propel blood forward 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.
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