how does my heart pump blood?

1the heart

Your heart is a fist-sized muscle that beats about 100,000 times a day, squeezing blood through your whole body.

2four chambers

It's really two pumps side by side, each split into an upper chamber and a lower chamber.

3blood comes in

Tired, low-oxygen blood comes in from the body, enters the right side, and gets sent to the lungs to reload on oxygen.

4blood goes out

Freshly oxygenated blood returns, enters the left side, and gets blasted out through the aorta to feed every cell in your body.

5valves click shut

Little one-way valves between chambers snap shut after each squeeze — that snap is the 'lub-dub' sound you hear with a stethoscope.

6the full loop

Zoom out and it's one big loop: heart to lungs for oxygen, back to heart, out to the body, and home again — forever, without you thinking about it.