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The cardiovascular system is the body's transport network: the heart, blood vessels, and blood that deliver oxygen and nutrients to every cell and carry away waste. Learn its anatomy, how circulation works, common conditions, and evidence-based ways to keep it healthy.
Reviewed & updated
The cardiovascular system (also called the circulatory system) is the body's internal transport network. It consists of the heart, a vast system of blood vessels (arteries, veins, and capillaries), and the blood that moves through them. Working together, these parts deliver oxygen and nutrients to every cell, carry away carbon dioxide and metabolic waste, distribute hormones and immune cells, and help regulate body temperature and fluid balance.
At its center is the heart, a muscular pump roughly the size of a fist. In an adult at rest it beats about 60–100 times per minute, and at a typical resting cardiac output of about 5 liters per minute it circulates the body's entire blood volume in roughly one minute. The blood vessels form a closed loop that, laid end to end, would stretch for thousands of miles, reaching nearly every tissue in the body.
Blood travels through the body in two connected circuits, both driven by the heart.
One-way heart valves keep blood moving in the correct direction. The tricuspid and mitral valves sit between the atria and ventricles, while the pulmonary and aortic valves guard the exits to the lungs and body. The "lub-dub" of a heartbeat is the sound of these valves closing.
Gas and nutrient exchange happens in the capillaries — vessels so thin (a single cell layer) that oxygen, glucose, and waste can pass directly between blood and tissue.
The heartbeat is coordinated by the heart's electrical conduction system, beginning at the sinoatrial (SA) node — the natural pacemaker — and is fine-tuned by the autonomic nervous system, hormones, and blood volume.
Cardiovascular disease is the leading cause of death in the United States. According to the CDC, about 919,032 people died from cardiovascular disease in 2023 — the equivalent of 1 in every 3 deaths — and one person dies from it about every 34 seconds.
Much cardiovascular disease is influenced by modifiable factors. The American Heart Association summarizes the essentials in "Life's Essential 8" — four behaviors and four health measures:
These steps are associated with lower risk of heart attack, stroke, and other complications. This article is for general education and is not a substitute for personalized medical advice — talk with a qualified healthcare provider about your individual risk and before making changes to your health routine.
In-depth, independently reviewed guides to the major organs and structures of this system.
This guide draws on 16 peer-reviewed and authoritative sources (StatPearls, NIH/NHLBI, MedlinePlus, and primary literature).