Located in the thoracic cavity, the heart is a four-chambered muscular organ that serves as the primary pump or driving force within the circulatory system. The heart contains a special form of muscle, appropriately named cardiac muscle, that has intrinsic contractility (i.e., is able to beat on its own, without nervous system control).

The chamber of the hearts are divided into two upper (superior) atrial chambers and two thicker-walled, heavily muscular inferior ventricular chambers. The right and left sides of the heart are divided by a thick septum. The right side of the heart is on the same side of the heart as is the right arm of the patient. The atrial and ventricular chambers on each side of the septum constitute separate collection and pumping systems for the pulmonary (right side) and systemic circulation (left side). The coronary sulcus or grove separates the atria from the...