Heart Anatomy
Four chambers, four valves and about 100,000 beats a day. How the heart is built and how one heartbeat actually works.
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Anatomy Category
Heart & Circulation
The pump that never rests and the 100,000-kilometre road network it serves — the heart, blood and blood vessels.
Guides
Guides in Heart & Circulation
Start with any guide below — each one is written for beginners and builds on the last.
Practice
Related tools
Reinforce what you learn with these interactive tools.
Calculator
Heart Rate Calculator
Estimate maximum and resting-based target heart-rate ranges to understand how exercise intensity is described.
4.8
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Calculator
Pulse Zone Calculator
Break the heart-rate range into training zones to see how "easy" and "hard" effort are defined.
4.8
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Interactive
Body Systems Explorer
Browse all major body systems in one place and jump to the organs and guides for each.
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Related articles
Deeper dives and fascinating facts from the blog.
Surprising Heart Facts: The Organ That Beats 100,000 Times a Day
The heart pumps enough blood in a lifetime to fill a supertanker. Explore the facts behind the body's tireless pump.
How Blood Travels the Body in Under a Minute
One drop of blood completes a full loop of the body in about a minute. Here is the route it takes and why.
Explore another body system
Every part of the body connects to the rest. Browse all nine categories and keep exploring.