Cardiac muscle
Cardiac muscle is a type of involuntary striated muscle
Striated muscle
Striated muscle tissue is a form of fibers that are combined into parallel fibers. More specifically, it can refer to:* Cardiac muscle .* Skeletal muscle* Branchiomeric muscles...

 found in the walls and histologic foundation of the heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

 and smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

. The cells that comprise cardiac muscle, called myocardiocyteal muscle cells
A cardiac muscle cell or myocardiocyte is the myocyte specific to the myocardium . Each myocardial cell contains myofibrils, which are long chains of sarcomeres, the contractile units of the cell...

, can be mononuclear or binuclear.

Coordinated contractions of cardiac muscle cells in the heart propel blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 out of the atria and ventricles
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...

 to the blood vessels of the left/body/systemic and right/lungs/pulmonary circulatory system
Circulatory system
The circulatory system is an organ system that passes nutrients , gases, hormones, blood cells, etc...