The circulatory system (also called the cardiovascular system) is the organ system that circulates blood throughout the body, delivering oxygen and nutrients to tissues and removing waste products including carbon dioxide. It consists of the heart (the pump), the blood vessels (arteries, veins, and capillaries), and the blood itself.
The circulatory system has two interconnected circuits. The systemic circulation carries oxygenated blood from the left heart via the aorta and arteries to the body’s organs and tissues, and returns deoxygenated blood through the veins to the right heart. The pulmonary circulation carries deoxygenated blood from the right heart via the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen, and returns oxygenated blood to the left heart.
When cardiac arrest occurs, this circulation ceases entirely, depriving all tissues of oxygen. CPR maintains a small amount of circulation to the brain and vital organs, and is the bridge to definitive treatment with defibrillation or advanced resuscitation. The brain begins to sustain irreversible damage within 4 to 6 minutes of complete circulatory arrest, which is why immediate response is so critical.
Disorders of the circulatory system (cardiovascular diseases) are the leading cause of death globally, including coronary artery disease, heart failure, stroke, and peripheral vascular disease. Risk factor management, including blood pressure, cholesterol, blood glucose, smoking, and weight, is central to preventing cardiovascular disease and reducing the risk of cardiac arrest.
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