Tap any part. Follow the blood.
Focus on the right or left side, click any chamber, valve or vessel to learn its job, and watch oxygen-poor and oxygen-rich blood pulse through a beating heart. Set the rate on the live monitor and take the guided tour of the whole circuit.
Four doors, one direction.
Blood moves through the heart in one direction only, and these four valves are why. Two sit between the atria and ventricles, two at the ventricles' exits — and their closing is the sound of a heartbeat. Tap a row to open that valve in the diagram above.
Four moves and you've read the heart.
Everything runs locally in your browser — nothing to install, nothing uploaded, nothing stored.
Pick your side
Focus on the whole heart, or isolate the blue right side or the red left side to study each circuit on its own.
Click any part
Chambers, valves, vessels — even the tiny pacemaker. Every part opens a dossier with its job and a quick fact worth remembering.
Drag & zoom
Drag to pan, scroll or pinch to zoom. The valves are small on purpose — get close and watch the blood squeeze through them.
Run the monitor
Set the heart rate and watch the ECG, the muscle and the blood flow respond — then take the guided tour of the whole circuit.
The heart, measured.
A muscle the size of your fist, doing the work of a pump a thousand times heavier. These are the numbers it keeps to.
The pump equation
Multiply beats per minute by the ~70 millilitres squeezed out per beat and you get cardiac output — the roughly five litres your heart pushes around your body every single minute. Crank the slider above and watch it climb.
A day in the life
That's enough blood shifted in 24 hours to fill about fifty bathtubs — done by a muscle the size of your fist, weighing less than a can of soda.
Built to last
Your heart started beating about three weeks after conception — before you had a brain — and will notch up around two and a half billion beats without ever taking a full second off.
Things people ask.
Everything about how the diagram behaves, how honest the drawing is, and what it saves (nothing).
Still stuck? Write to us — we read everything.
How do I use the interactive heart diagram?+
Pick a focus — the whole heart, just the right side, or just the left — then tap or click any chamber, valve or vessel to see what it does and a quick fact. Drag to look around, scroll or pinch to zoom, and follow the flow strip underneath to trace the blood's route step by step.
Is this heart diagram anatomically exact?+
No. It's a stylized anterior cutaway — the classic teaching view — built so every part is easy to spot, click and tell apart. Real hearts vary in size and shape, the chambers overlap in 3D, and the vessels enter from behind, not neatly from the sides.
How does blood flow through the heart?+
Oxygen-poor blood arrives from the body through the vena cavae into the right atrium, drops through the tricuspid valve into the right ventricle, and is pumped through the pulmonary valve and pulmonary artery to the lungs. Freshly oxygenated blood returns through the pulmonary veins to the left atrium, drops through the mitral valve into the left ventricle, and is fired through the aortic valve into the aorta — around the whole body.
What do the valves actually do?+
They're one-way doors. The tricuspid and mitral valves stop blood leaking back into the atria when the ventricles contract; the pulmonary and aortic valves stop it draining back into the heart between beats. Their slamming shut is the 'lub-dub' sound of a heartbeat.
Why is the right side blue and the left side red?+
Colour tracks oxygen, not the type of blood vessel. The right side of the heart handles oxygen-poor blood heading to the lungs — drawn blue — and the left handles oxygen-rich blood heading to the body, drawn red. That's also why the pulmonary artery is blue and the pulmonary veins are red.
What does the heart-rate slider change?+
It sets the beats per minute of the live monitor and the beating heart. The ECG trace, the pulse of the muscle and the speed of the flowing blood all follow it, and the readout shows the cardiac output that heart rate produces. Nothing is saved when you move it.
Does the tool save or upload anything?+
No. The diagram runs entirely in your browser. Nothing you click, zoom, or select is ever sent to a server, logged, or stored.
Can I use this on my phone or tablet?+
Yes. Tapping selects a part, dragging pans the view, and pinching zooms in or out, so the whole diagram works the same way with touch as it does with a mouse.
Is this interactive heart diagram free to use?+
Yes, it's completely free with no account, no sign-up, and no limit on how much you explore.