Today you are going to be learning about internal body systems, including the heart. The heart is an easy internal organ to start with when learning about the body because we can hear and feel the human heartbeat. Put your hand on your chest and hold very still, can you feel your heart beating?

Materials:

• • 2 small jars or cups
  • 2 Bendy Straws
  • Balloon
  • Scissors (with parent supervision!)
  • Toothpick
  • Tape/Glue
  • Water
  • Red Food Coloring (optional)

Directions:

1. 1. Fill your jar or glass halfway with water and add some red food coloring – this jar will represent your heart. The food coloring is optional, but it makes our experiment more blood-like. Take your balloon and cut the neck of it off. Take that top part, stretch it out a bit, and put it over the top of the jar so it is tight (save the neck part of the balloon for later). 
   2. Take a sharp toothpick and poke a hole in the top of the balloon once towards one side of the jar. Make a second hole about an inch away from the first. Parents, you will want to do this one or at least heavily supervise your child while it is happening. Scissors or a knife could also be used, but try to make the holes as small as you can.
   3. Take your straws and push one through each hole with the bendy part sticking out the top. You might have to push hard, but they should pop through. 
   4. Slide the neck part of the balloon onto one of the straws and tape it around the straw so the opening is closed.

Your pumping heart model is ready to get that blood flowing.

1. 1. Place a second cup under the open straw to catch the “blood” as it is pumped out.
   2. Push up and down on the balloon, between the two straws. Pumping quickly and firmly works best.
   3. You will be able to see the blood go up the open-ended straw and come out into the cup! Here we are simulating our heart pumping blood through our body.

The Science Behind the Experiment:

The pumping you do on the balloon mimics how the heart pumps in our bodies. The balloon on the straw works like the valves on the heart. It opens when you push down on the pump and closes as you release. This is what lets the blood flow up through the open straw, but like in the body, it prevents the backflow of blood.

Now, of course, this is a simplified model: the human heart has a lot more going on than just a single valve and two blood paths. But this is a great way to get a basic understanding of how our hearts pump blood throughout our bodies.

Activity credit: Team Cartwright