The short idea: The heart is a strong muscle that works like a pump. It relaxes to fill with blood, then squeezes to push the blood out into the blood vessels.
Step-by-step:
- Relax (fill): The heart opens its rooms and blood flows in, like a balloon or sponge getting full.
- Little doors shut: Tiny valves (like one-way doors) close so the blood does not go backward.
- Squeeze (pump): The heart muscles tighten and push the blood out into tubes called blood vessels.
- Two jobs: One side of the heart sends blood to the lungs to pick up oxygen. The other side sends oxygen-rich blood to the rest of the body so you can run, play, and grow.
- Repeat: The heart relaxes and fills again, then squeezes again — over and over. Each cycle is a heartbeat (you can hear it as "lub-dub").
Try this fun activity:
- Put your hand on your chest or your wrist. Count the beats you feel: 1-2-3... that is your heart working.
- Blow up a small balloon a little and let the air out slowly to imagine how filling and emptying feels.
The heart keeps blood moving so your body gets oxygen and energy — and it does this all day long!