Let’s Take A Trip Through The Cardiovascular System!

For the past two weeks, Kat and I have been learning about the cardiovascular system and how it works to keep our body alive and healthy. We’ve done some really great projects to demonstrate how the heart works, and we’ve even dissected a pig heart in our home! All of this will culminate into a visit with the American Red Cross, where we will learn more about human anatomy relating to the circulatory system, Kat will learn some basic CPR, and I will donate a pint of blood to the Red Cross!

In this post, I’ll talk about how the heart works, and share some of the wonderful projects we’ve been working on as we learned about the heart!

The heart is an incredible machine. Working tirelessly day and night, it pushes our blood throughout our entire body, even working against gravity to get our body the nutrition it needs to sustain itself!

The heart itself is divided into two halves, separated by a thick muscular wall called the septum. These halves are each divided into two sections, creating a total of four chambers in the heart. The top chambers consist of the left and right atria, while the lower chambers consist of the left and right ventricles.

When we breathe air into our lungs, tiny air sacs within the walls of the lungs (called alveoli) allow the oxygen to pass into the blood stream. This oxygenated blood travels from the lungs into the left atrium. The heart muscles contract, pulling the valves open, allowing the blood to be dumped into the left ventricle. The valve then slams shut, preventing the blood from flowing backward into the bloodstream. When the heart contracts again, it opens the valve from the left ventricle to the aorta, sending freshly oxygenated blood to the rest of the body!

Interestingly, the aorta is the largest artery in the human body, measuring about an inch in diameter! This artery is responsible for sending all of the oxygenated blood to our entire body (other arteries branch off the aorta). This blood moves fast, so the aorta must be incredibly thick and strong to be able to handle all of that pressure!

After leaving the aorta, red blood cells take the oxygen to various parts of the body and exchange it for carbon dioxide waste. This deoxygenated blood travels back to the heart where it enters the pulmonary trunk and is dumped into the right atrium. The heart contracts, pulling the valves open so the blood can fill the chamber of the right ventricle. From here, it is pumped out to the pulmonary arteries where it heads to the lungs. The blood cells then exchange the carbon dioxide for a fresh supply of oxygen. As we breathe out the carbon dioxide waste, the blood travels back to the left side to begin the process of circulation all over again!

After we had learned about the cardiovascular system and how it works, I wanted to find a way to really demonstrate the flood of blood. So, we printed out and played with our own model of the circulatory system!


Materials Needed:

Large flat surface
Printed pictures of red blood cells
Printed pictures of the heart and other body organs


1. Do a Google Image Search for diagrams of various organs (Tip: turning on “safe search” filters will avoid images of organs in surgery!). Exercise your child’s knowledge of anatomy by inviting him/her to choose the organs you search for!

2. Save and print your pictures. We printed ours as 3.5 x 5, so they would all be the same size. You will want to print several copies of the red blood cells, since you’ll be using a lot of them to represent blood.

3. Cut out your pictures!

4. Have your child lay the organs out on a flat surface. Have him/her place them in the order they would occur in the human body.

5. Using the red blood cells, make a path from the left side of the heart to the rest of the organs! As you move the blood cells about, talk about how they’re carrying oxygen to the organs.

6. Once they arrive, pretend that they pick up carbon dioxide. Now take them to the other side of the heart where the waste can be expelled through the lungs!

While talking about blood circulation, it helps to know exactly what the blood is carrying to and taking from the various muscles, organs, and tissues of the body. Here is a fantastic video by the band, They Might Be Giants, from the album Here Comes The Science. This song is all about blood, how it moves, and what it does!

Once we had finished our model of blood flow, it was time to start thinking about how the heart actually pumps blood. We wanted to make a working model of a pump to demonstrate the how the heart acts as a pump to get our blood moving!


Materials Needed:

Beaker or wide mouthed jar
Red Food Coloring
2 Flexible straws
Toothpick or scissors
Large pan or sink
Note: This post contains affiliate links to products.


Fill your jar halfway with water. Add red food coloring to resemble blood.

2. Cut the neck off the balloon, where it starts to widen. Stretch the balloon to soften the rubber and set the neck piece aside.

3. Stretch the balloon around the rim of your beaker or jar. Pull it down as much as you can, leaving a smooth, flat surface over the top of your container.

4. Using the toothpick (scissors worked much better for us), make two very small holes in the balloon, approximately one inch apart. You want the holes only large enough to fit the straw through, and it should tightly seal around the straw.

5. Put the straws in the holes, bending the neck downwards. If you cut the hole too large, use tape to seal it so air doesn’t pass through.

6. Use tape to secure the neck of the balloon around one of the straws. Make sure that no air can pass through the straw.

7. Point the open straw downward and start pumping! The neck of the balloon over one of the straws acts as a valve, blocking any of your blood from flowing back through the “plumbing system”. The other straw allows blood flow to pass through, where in a heart, it will continue through the aorta to the body or pulmonary arteries to the lungs!

Now we had a much better understanding of how the heart beats to pump blood throughout our bodies! We’ve moved blood cells around in circulation and made our own pump to represent the heart beating! But we still didn’t have a precise knowledge of the anatomy of the heart. Really knowing that would help us greatly in really internalizing how it all works. To that end, we made our own anatomical model of the human heart!


Before you begin, it helps to look at a diagram of the human heart for proper placement of the arteries. We used our copy of Usborne’s Illustrated Book of Biology to help us with our placement. You can use any medical reference book, or search for diagrams on the internet.

Materials Needed:

Modeling clay (red and blue)
Aluminum foil
Hot glue gun
Pipe cleaners
Red crepe paper (you can also use paper mache)
Rolling pin
Milkshake straw


1. Cut your milkshake straw into artery pieces and set them aside. You will need five ½” pieces, three 1” pieces, and two 2” pieces.

2. Use your aluminum foils to make medium sized balls:. One should be the size of a tennis ball, the other two should be the size of a golf ball.

3. Firmly press 3 toothpicks into the upper left corner of the larger ball. Use the hot glue to secure them in place. Then attach one of the smaller balls to it. Do the same for the other side until you have a mouse shape with your foil balls.

4. Cover the rolling pin with aluminum foil, so the clay will not stick to it. Then use your rolling pin to roll some sections of red clay into a flat, pliable shape. Use this clay to cover your foil. Press it in firmly, so it sticks to the foil. Cover your foil pieces with clay until it begins to look like a human heart. Continue shaping and smoothing the foil and the clay until you are satisfied with how it looks.

5. Once you’re finished with the shape of the heart, it’s time to start on the aorta! Hold 6 pipe cleaners tightly together, then bend them in half so that they fold in on each other. Use the hot glue to secure the ends in place, so they do not pop open.

6. Bend the folded pipe cleaners into a U-shape. Wind the crepe paper around the pipe cleaners until they are fully covered. Use hot glue to secure them in place.

7. Stick 3 toothpicks on one end of U-shaped pipe cleaner. Glue them in place and stick the aorta into the top of the heart, at the center of the bend. Bend the U-shape so that it ends behind the right side of the heart and glue it into place.

8. Now it’s time to work on the pulmonary trunk! Take 3 pipe cleaners and bend them in half so they fold in on each other. Use hot glue to secure the ends together. Bend the pipe cleaners so that they have a slight curve. Then use the red crepe paper to cover the pipe cleaners, and glue them into place.

9. Stick 3 toothpicks in one end of the pulmonary trunk. Firmly press the toothpicks into the top left side of the heart, using hot glue to secure them in place. Bend the pulmonary trunk so that it hugs the aorta, and bends slightly behind it. Use glue to secure one of the ½’ pieces of straw to the end.

10. For the pulmonary arteries, take 2 pipe cleaners, and bend them together as you did for the aorta and pulmonary trunk, using glue to secure the ends together. Wrap it with crepe paper and use glue to secure it in place. Thread this through the loop of the aorta, and behind the pulmonary trunk. Use your glue to secure it in place, then use glue to attach two ½” pieces of straw to each end, making a V shape.

11. Now it’s time to work on the arteries! Grab a milkshake straw and cut it up! You’ll need five ½” pieces, three 1” pieces, and two 2” pieces.

12. Now, it’s time to connect the last of your arteries! The 1” pieces should be spaced evenly apart along the top of the aorta. Finally, the 2” pieces should stick out of the right side of the heart.

13. Finally, roll out some blue clay into thin strips, and line the bottom of your heart with some posterior veins!

Now you’re finished with your very own anatomical model of the human heart! Congratulations and great job!

Learning about how our heart works and our blood flows throughout our body was a fascinating experience. One of the coolest things we learned was that not only are there valves in the heart, but there are valves in our veins too! It was really neat to think about how our blood flows through arteries and veins, what the role of blood is in our body, as well as how hard our heart works to pump it through so many thousands of miles of blood vessels every second!

We also now have a gorgeous model of the human heart that WE made, sitting on display in our science library at home! Whenever we look at it, we can proudly remember how much time we put into making it, and appreciate our heart for working continuously as it does.

We also learned even more when we dissected a heart in our kitchen! Due to the amazing experience, we had with the dissection, that took a whole new blog post! Here’s the link where you can see what we did and find out how to get your own heart dissection kit!



  1. cool blog! I am going to use this for a science project!

  2. haha YES that's what it amounted to haha However if you had actually said how long it took, I wouldn't have even bothered to try so what you said was great!

    I hope he remembers – or that if we go back and do this fun project again in a few years we'll BOTH be better at it. 🙂

    Thanks again for your wonderful posts. Hands-on is where it sticks!

  3. Awww that's so wonderful!!!! Reading this totally just made my morning, I'm so glad it worked out! It's so funny how these things can be such a trial and error, right? "Just put some clay on your foil" really translates to "spend a half hour trying desperately to make a heart shape and *finally* getting it right!" 🙂

    I'm so, so happy that you guys spent your Valentine's Day learning about the heart and how it works, and appreciating how amazing it is that our hearts pump continuously for our whole lives, keeping us alive! That's incredible!

    Great job rockin it out with your crafting skills with your son! I bet he really enjoyed it, and he'll remember doing this with you when he gets older! You Rock! <3 🙂

  4. We love They Might Be Giants! You made the heart project seem so … easy. It was not! BUT we charged through, despite my poor crafting abilities, and not having enough clay and having to start over haha Thank you for sharing this! My son learned a lot on Valentine's Day about the human heart and blood vessels! I love reading your posts and getting excited about Science with you.

  5. please help me, i need to give the project of the working model of our heart day after help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  6. Can you use playdough instead of clay for the model heart?

  7. Wow this is an incredible post AND my 5 yr old even sat beside me to WATCH Thee entire video!! Amazing! She never Sista through educational videos well–this was perfect. She really understood it! Time for a heart mobile shopping trip!

  8. I'm glad to see so many helpful tips right here. Thank you

  9. Just answered my own question. I just found your blog and I'm really enjoying it. My triplet grandsons and I are taking a "journey" through the human body this summer, and I'm definitely going to "borrow" some of your experiments. Thank you for sharing!

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