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Author(s): David R. Caprette, PhD
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Diagram of the Human Heart

The two atria are the receiving chambers of the heart. The thick-walled ventricles are the pumping chambers. Blood is collected from the body and emptied into the right atrium. Blood in the right atrium passes through the tricuspid valve and into the right ventricle. The right ventricle then contracts and forces blood through the right pulmonary valve, into the pulmonary arteries and on to the lungs (pulmonary circulation).

After oxygenation in the lungs, the blood is returned to the left atrium through the pulmonary veins. From the left atrium, blood flows past the mitral valve into the left ventricle through the aortic valve and out to the body through the aorta (systemic circulation).

The rhythm of the heart is initiated in the sinoatrial node, often referred to as the "pacemaker" of the heart. The impulse spreads and is picked up by the atrioventricular node. The autonomic nervous system can change the pace of the heart rate but cannot initiate it.

The health of the heart and blood vessels can be monitored by pulse, blood pressure and electrocardiograms.