A guide to the
Heart.
The 3D heart can't be shown in this browser, but every word of the story is here.
About the size of your fist. Beats about 100,000 times a day. Never takes a break.
Scroll to look insideSmall. Strong. Right in the middle.
Your heart sits in the middle of your chest, tilted a little to the left, protected by your ribs. It's a muscle about the size of your fist, and it grows as you grow.
A lifetime of work.
- 100,000beats a day
- 5litersabout all the blood in an adult's body, pumped every minute
- 1minuteabout how long blood takes to travel all the way around your body
- 0days off
Four rooms. Two jobs.
Inside are four hollow chambers. The two on top, the atria, collect blood as it comes in. The two on the bottom, the ventricles, squeeze hard to push it out. A thick wall down the middle, the septum, keeps the right side and the left side apart.
Right and left are named from the heart owner's point of view (yours!), so the right side is on your left when you face someone.
Two pumps, side by side.
The right side pumps blood a short way, to the lungs, where it picks up oxygen. The left side pumps it all the way around your body. Every drop takes both trips, over and over.
The trip goes: body → right side → lungs → left side → body.
- Low in oxygen
- Rich in oxygen
Lub — the doors between the top and bottom rooms
Dub — the doors out to the arteries
One-way doors.
Four valves work like one-way doors. When the bottom chambers squeeze, the doors between the top and bottom rooms snap shut: “Lub.” When they relax, the doors out to the big arteries snap shut so blood can’t slide back: “Dub.” That’s your heartbeat: doors closing.
It all starts with a spark.
A tiny patch of cells at the top of the right atrium, the natural pacemaker, sends out an electrical signal. It spreads over the top chambers, pauses for a split second at a checkpoint between the top and bottom chambers, then races down to the bottom ones. No thinking required.
This is the signal a doctor sees on an ECG, a test that reads it through stickers on your skin.
It keeps pace with you.
Your heart speeds up when your muscles need more oxygen and slows down when you rest. A surprise can speed it up in seconds: your nerves flip the switch, and adrenaline, a chemical messenger, says “get ready to move.”
Sleeping, 55 beats a minute
Typical for an adult. Children's hearts beat faster.
Now it's your turn.
Spin it. Slow it down. Look inside.
Drag to rotate. Tap a part to see what it is.
The interactive heart needs WebGL, which this browser doesn't have turned on.
A flat picture instead of the 3D heart: dark red is low in oxygen, bright red is rich in it.