How to Make a Pumping Heart Model

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The heart is a special muscle that sends blood around your body. How exactly does the heart pump blood? 

My kids have been interested in the heart ever since we made the DIY stethoscope. This pumping heart model was a great follow-up to the heartbeat activity! 

Pumping Heart Model Flow Blood

Before each heartbeat, the heart fills with blood. Then its muscles contract and squeeze blood into the arteries, the blood vessels that carry blood away from the heart. 

To understand how the blood beats, the pumping heart model will demonstrate the chambers and values of the heart. Ready for your child to squeal with delight as blood squirts out of the straw! I know, weird sentence, but science is fun!

How to Make a Heart Model


  • Mason jar or glass
  • 1 small water balloon
  • 1 large balloon
  • Water
  • Red food coloring
  • 2 plastic straws
  • Rubber bands or tape
  • Scissors
  • Tray


1. Fill the mason jar about ⅔ full with water.

2. Add red food coloring and mix.

3. Cut the neck off the balloon.

4. Stretch the body of the balloon over the opening of the jar. The balloon should be as tight as possible. Secure the balloon to the jar with a rubber band.

Pumping Heart Model Balloon

5. Cut two small holes in the balloon. They should be smaller than the straws so no air escapes from the holes when you push on the balloon.

6. Slide the small water balloon onto the end of one of the straws. Secure with a rubber band or tape.

Pumping Heart Model Balloon Straw

8. Push both straws through the holes of the balloon.

9. Set the heart model in a tray to catch the “blood.” Make sure to bend the straws downward to avoid projectile blood!

Pumping Heart Model Setup

10. Gently press the center of the stretched balloon to pump the blood out of the jar.

Pumping Heart Model Blood Flowing

How the Pumping Heart Model Work

Our hearts are made out of the left chambers and right chambers. The top chambers are called the atrium, which fill with the blood returning to the heart from the body and lungs. The bottom chambers are the ventricles, which squeeze and pump blood out of the heart.

Each chamber also has valves that control the flow of the blood. When the valves open up, the blood flows from the atrium to the ventricle and out of the heart. The valves prevent the blood from flowing backward from the ventricle to the atrium.

In the heart model, the mason jar is already filled with blood. When you press down on the balloon, or the muscle of the heart, blood squirts out. 

The small water balloon acts like the valve and keeps the blood flowing in the right direction. If you remove the balloon, you will find that while water still comes out of the straw, the water remaining in the straw also flows back into the jar after you release the tension on the balloon.

For more fun human anatomy activities, check out:

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