How can you tell when Valentine’s Day is approaching? All those red heart-shaped boxes of chocolate in the store aisles are a good clue! Speaking of heart-shaped, are those boxes of chocolate actually shaped like the heart inside your chest?

As it turns out, the traditional shape of a heart doesn’t bear a very close resemblance to your real human heart. Some believe it resembles a cow’s heart, but even those people will admit that the resemblance isn’t very strong.

Others believe that the human heart may have been the inspiration for the traditional heart shape, since philosophers from ancient times have equated the human heart with the center of emotion. Perhaps these ancient philosophers simply took the shape of the human heart and made it more attractive.

Still others believe the traditional heart shape may have come from the shape of the seed of the Silphium plant. Widely used in North Africa as a seasoning thousands of years ago, this plant is now extinct. Historians believe it did play a big role in the economy of ancient Egypt, and its distinct heart shape was used often on coins.

Whatever the source of the modern heart shape, today that shape represents love and strong emotion. This is only appropriate, given how important the heart is to the human body.

Your heart is actually a muscle about the size of your fist. Located just a bit to the left of the middle of your chest, your heart muscle constantly contracts to pump blood throughout your body.

It’s actually like two pumps in one. The right side of the heart receives blood from the body and pumps it to the lungs. The lungs refresh the blood with oxygen. The left side of the heart then receives the blood from the lungs and pumps it back out to the rest of the body.

Your heart is made up of four chambers: two on the top (called atria) and two on the bottom (called ventricles). They’re separated by a thick wall of muscle called the septum. The atria and ventricles work together. The atria fill with blood returning from the body or the lungs, while the ventricles push out the blood to the lungs or the rest of the body.

Special valves in the heart open up to let blood pass through and then quickly close to keep blood from flowing backward. These valves keep your blood constantly pumping forward in the same direction.

As your heart pumps blood through your body, it travels through blood vessels called arteries and veins. These blood vessels, along with your heart and lungs, make up your body’s circulatory system. Your circulatory system transports blood full of oxygen and other important nutrients to all the areas of your body that need them.

129 Join the Discussion

1 Star2 Stars3 Stars4 Stars5 Stars  (39 votes, avg. 4.13 out of 5)
  1. Thoughts: Will your heart change color if it’s not working correctly? We were very intrigued by the different ways hearts are found in the world. (P.S. Happy Valentine’s Day WONDERopolis.)

    Connection: We’re WONDERing about Darth Vader in Stars Wars and if his appearance was effected by his heart. We want you to know that our P.E./heatlh teacher, Mr. Radcliffe has taught us all about the heart and circulatory system.

    Prediction: Where did Bingo get its name? How many different kinds of islands are there? What are vitamins made of? Do vitamin help keep us healthy? Where did Bingo originate? Is Bingo more fun than a casino game? Have you ever played Battleship? How do you play Bingo? Do you play Bingo?

    • Good morning, Wonder Friends in Mrs. Hess’ Class! We really love your three-step approach to WONDERing (thoughts, connection, prediction)! We think it’s inspired other WONDERers, too! :-)

      Our hearts are red inside our bodies because our hearts are pumping blood and oxygen through our bodies, keeping us nice and healthy. If a heart stops working, the color will change, it will no longer be bright red. We hope you’re having a great Valentine’s Day today– thanks for sharing your SUPER comment!

      We think your connection to today’s Wonder is great, too! From Star Wars to physical education, you’ve been doing a great job of WONDERing today! We look forward to WONDERing with you again, we think tomorrow’s Wonder will be a winner! :)

  2. We are glad that valentines are not actually shaped like human hearts. We would not want to give human heart shape valentines to our friends. It would also be hard to cut out a human shaped heart.

    We think tomorrow’s wonder will be about bingo.

    • Great point, Wonder Friends in Ms. Bayko’s Class! We think cutting out the shape of human hearts would be a bit difficult, so it’s a good thing we can share Valentine hearts with one another today! Hope you’re having a great day celebrating friendship and love! See you tomorrow! :)

    • We sure do agree, Wonder Friend Kate! We are happy to learn that our hearts pump blood to the rest of our bodies, keeping us healthy and allowing us to do what we do everyday! :)

    • Nice work, Wonder Friend Olivia! We’re happy you have been WONDERing with us today, especially on such a fun Valentine’s Day! It’s amazing that a muscle the size of our fist can pump blood to our entire body! We think the heart is pretty cool! Thanks for sharing your comment! :)

  3. Dear Wonderopolis,

    Happy Valentine’s Day! We learned how the heart works. We went on to Youtube to see what a real heart looks like and how it works. It was an animated video so we still wonder what an actual heart looks like. We learned that blood is blue until it gets oxygen from the lungs. We think tomorrow’s Wonder is about Bingo. We play Bingo once a month at our school to raise money for a school in Africa. We also think it could be a grid coordinate.

    • Good morning, Wonder Friend in Mrs. Chevalier’s Class! Happy Valentine’s Day to you, too! We’re so glad to hear that you continued to Wonder about the human heart! Nice work!

      We look forward to finding out what tomorrow’s Wonder will be, too! We think a bingo fundraiser sounds like a great way to help others in need! We are so proud of all of you! :)

    • Thanks for sharing your comment and including a special heart for us, too, Mrs. Roberts’ Class! We’re so happy that you are visiting us today! Happy Valentine’s Day to you as well, we’re glad your day is filled with Wonder! :)

    • Thanks for being great Wonder Friends, Mrs. Hunt’s Class! We are impressed to learn that our heart is pretty small, but it does a LOT of work to keep our body healthy! Thanks for joining us today! Happy Valentine’s Day, Wonder Friends! :)

  4. Happy Valentine’s Day!! Thank you for today’s wonder. We never thought about where the traditional heart shape came from. You always give us something to think about.

    We think the next wonder will be about Bingo and how it was invented.

    • Happy Valentine’s Day to you, Wonder Friends in Mrs. S’s class! We’re glad today’s Wonder made you think about the connection between the human heart and the symbol of love! We are happy to hear that you’re thinking outside the box and exercising your imaginations! We look forward to WONDERing with you again, soon! :)

    • HOORAY, we’re happy that you had the same Wonder, Michael! We’re glad to know that you learned something new with us today, and we hope you’ll come back to Wonder with us again! :)

    • Well thank you so much for sharing your cool comment, Abigail! We sure do love WONDERing with a great friend like you! Happy Valentine’s Day! :)

    • We’re so glad to hear it, Kathy! Thanks for sharing your awesome comment and we hope you have a SUPER Valentine’s Day! :)

  5. We were surprised to hear that our heart is not shaped like the heart symbol.

    Though the heart shape we know is just a symbol, we know it represents something much bigger- love.

    We LOVED the video, especially the egg, bacon, and building with the lights on. We would add the shape of a heart with our hands (like Taylor Swift does), a heart with a peace sign, a box of chocolates, a real Valentine, and baby feet shaped like a heart!

    Thanks for the WONDERful information today!

    • We’re so happy to hear you learned something new, Mrs. Lawinger’s Law Enforcers! We liked learning about symbols of love and how it connects to the heart! Today’s Wonder recipes are making us hungry! Thanks for sharing some of your favorite heart shapes from today’s Wonder, we hope you have a SUPER Valentine’s Day! :)

  6. Dear Wonderopolis,

    Happy Valentine’s Day! We LOVE Wonderopolis!

    We learned that there are four chambers in the heart called the ventricles and atria. If there wasn’t blood in the heart, it would be clear. The heart is not actually shaped like a heart.

    We have also been reading “heart” idioms today. One of our favorites was “Wearing your heart on your sleeve.”

    We are off to P.E. to exercise our hearts!

    Ms. Uppena’s Third Grade Super Sleuths

    • Happy Valentine’s Day, Super Sleuths! We’re so glad you’re here today! Thank you for sharing what you learned about ventricles and atria!

      We liked that you mentioned idioms… we hope you’ll enjoy this Wonder from the past: Wonder #85– Why Do People Say “Under the Weather”? :)

  7. Our 5th graders weren’t tricked by the question! We used our background knowledge and knew that hearts weren’t shaped like hearts. It was interesting to read and learn about the other theories of the heart shape. We made a connection to Miss Klish’s nephew who was born with a heart defect. His heart doesn’t pump like ours, and he has needed a lot of surgeries to get it to work better. Happy Valentine’s Day Wonderopolis!

    Our guesses for tomorrow included: BINGO, Battleship and board games.

    We’ve enjoyed learning new things through Wonderopolis. It’s a great way to start our day. :)

    • WOOHOO, we’re so happy our Wonder Friends in Miss Klish’s 5th Grade used background knowledge and context clues to correctly answer today’s Wonder! YOU ROCK! :)

      We are thinking of Miss Klish’s nephew, and we hope all his surgeries are successful and great! Thanks for WONDERing with us this Valentine’s Day! We look forward to sharing our day with you, too! See you soon! :)

  8. We loved all the hearts in today’s video! We didn’t know that we could find so many hearts in different places. Happy Valentine’s Day from our class!

    • It’s great news that you enjoyed today’s Wonder, Ms. Pressley’s Class! We bet you’ll see the shape of a heart in places you never thought possible from now on! Perhaps you can make a heart for one another today, in honor of Valentine’s Day! We hope your day is WONDERful, just like you! :)

    • Nice work, Wonder Friend Jonathon! We learned that the heart in our body is not the same shape as the heart we see on Valentine’s Day! We are so glad you’re here today! :)

    • We think you’ll learn all about the different types of heart symbols in today’s Wonder, Crystal! Those cool sticker hearts are a mirror image of one another– if you fold a heart in half it will be perfectly lined up. The heart, which is a super strong muscle, is shaped more like a fist! Take a look at today’s Wonder video and article, we think you’ll learn a lot! Happy Valentine’s Day! :)

    • We sure are glad you think so, Jenna! Thanks for sharing your comment and WONDERing about all kinds of hearts with us! Have a SUPER Valentine’s Day! :)

  9. I think that our hearts are not really not shaped like a sticker I just think that whoever made up the sticker heart just thought that our real hearts looked like that.

    • That’s a great prediction, Diego! We learned that no one is quite sure where the symbol for the heart came from, but we have a few guesses! Thanks for sharing your comment! Have a great Valentine’s Day! :)

    • Hey there, Jusin, thanks for visiting us today! Happy Valentine’s Day! The human heart looks a lot different than the heart you might see on Valentine’s Day cards! We Wonder why that is… and you can learn more about it in today’s Wonder! Check out the video, too, we think you’ll enjoy it! Have a stellar day! :)

    • We are so happy we’ve got hearts, too, Sydney! It’s so cool to learn about the super muscle that helps keep up healthy! Thanks for sharing your comment today! :)

  10. Dear Wonderopolis,
    We love reading your wonder each day. We are wondering if you can help us understand why our blood looks blue under our skin, but red if you cut yourself.

    Happy Valentine’s Day!

    Ms. Rehnke’s 2nd Grade Class

  11. Hi Wonderopolis! I’ve been always WONDERing if your heart is really shaped as a real heart! That is a great WONDER of the day! HAPPY VALENTINES DAY!! :)

    • HOORAY for today’s Wonder, Emily, we’re glad it answered your question! Happy Valentine’s Day to you! Have a super day! :)

  12. I loved to learn that all those things on that video could make hearts. It was the most amazing thing I’ve ever seen. I learned that your heart pumps blood throughout your body. Pretend hearts are cute, a real heart is gross. Tomorrow’s Wonder of the day might be about a waitress calling out a restaurant table.

    • We love your enthusiasm, Zoe! Thank you for sharing what you learned about the heart today! It’s great that you enjoy pretend hearts, especially on today’s special Valentine’s Day! We look forward to WONDERing with you again! :)

    • We’re so glad to hear it, Brooke! Thanks for WONDERing about the most important muscle in our body… but we think many others agree with you about pretend hearts! Happy Valentine’s Day! :)

  13. Hi Wonderopolis! Happy valentines day!!! I loved today’s wonder!!! I thought the video was great!! !I did not know that your heart is made up of four chambers!!!

    • Happy Valentine’s Day to you too, Holly! It’s so cool that you learned about the different chambers of the heart. What a perfect day for WONDERing about the heart! :)

  14. Hi Wonderopolis Happy Valentines day! ! ! !

    I loved the WONDER of the day ! ! ! ! I thought the video of the day was so cool ! ! ! ! I learned that hearts are not shaped like I thought!

    • Happy Valentine’s Day to you, Alicia! Thanks for sharing your thoughts and what you learned about hearts of all sorts! We like your enthusiasm! :)

  15. Wonderopolis, I think that this is a great wonder for valentines day! There is so many places a heart can be! I don’t think the human heart is shaped like the one we draw. I predict the next wonder of the day is about bingo. This is wonderful learning program for kids!

    • Hey there, Merebear! We just love your comment– hearts appear everywhere! Isn’t it cool that the human heart and the Valentine’s heart are so different? We hope to Wonder with you soon! :)

  16. Hi wonderopolis I enjoyed learned a lot about hearts I really didn’t know a lot about hearts I did know that it was not shaped as a box of chocolate and I learned a lot about hearts.

    • It’s awesome that you learned some new facts about the heart today, Jewels! We think chocolate-shaped hearts are delicious, especially when you can share them! Thanks for sharing your comment today! :)

  17. Hi Wonderopolis! It is so interesting that so many things are shaped like hearts. No, hearts are not shaped like hearts, they are shaped like fists. I am really looking forward to finding out what tomorrow’s wonder is!

    • Great work, Wonder Friend Olivia! Our human hearts are shaped like fists, but the symbol of love looks much different! Thanks for telling us about what you learned today! See you tomorrow! :)

  18. What a great Wonder for Valentine’s day!!

    What does your heart really look like??

    Is your heart really red?

    Why do we have 4 holes in our heart?

    What does the heart sound like?

    • Happy Valentine’s Day to you, Wonder Friends in Mrs. Piccioni’s Second Grade Class! We are happy to hear that you joined us today! It looks like you’ve been doing an awesome job of WONDERing even further about the heart! WAY TO GO! We know that our hearts are red because it’s responsible for pumping blood throughout our body! Check out this Wonder from the past… it’s right up your alley!
      Wonder #519– If Blood Is Red, Why Are Veins Blue?

      We Wonder if you have heard your own heart beating… perhaps after running in P.E. class or during a soccer game?

      We look forward to WONDERing with you again! :)

    • We’re really glad to hear that this Wonder made your heart skip a beat, Wonder Friend Berkleigh! Thanks for sharing your thoughts about our heart Wonder today! We hope your Valentine’s Day was WONDERful, just like you! :)

    • SUPER guesses! Thanks to our Wonder Friends in Miss O’Keefe’s Class, we are WONDERing what letters and numbers go together?! Thanks for sharing your comment today! :)

    • We like your style, Wonder Friend! Thanks for making us smile and using “heart” in such a creative way! Happy Valentine’s Day! :)

  19. Dear Wonderopolis,
    I learned that your heart is the size of your hand when you make a fist. I think tomorrow’s wonder is Bingo.

    • Thanks for sharing your awesome comment, Reagan! We are glad you shared what you learned about the human heart today– we think it’s very impressive that such a small muscle can do so much! We can’t wait to find out what tomorrow’s Wonder will be! HOORAY! :)

    • Thanks for sharing your awesome comment, Wonder Friend Daelynn! We are so glad that you and your sister are WONDERing together! HOW COOL! Happy Valentine’s Day, Daelynn! :)

    • Thank you so much for WONDERing with us, Alisa! We are glad to know today’s Wonder video made you smile! We sure hope to see you soon! :)

  20. Dear wonderopolis

    I really thought that the video was nice we also wached a video off yutube about how the heart works. I think that tomorrow’s wonder is the bingo caller! Wonderopolis best site ever!

    • Hey there, Pablo! We think it’s great that you and your Wonder classmates did some more exploring about the human heart today! Mrs. Chevalier must be a WONDERful teacher! :)

      Thanks for telling us how much you enjoy Wonderopolis– we are so lucky to have awesome Wonder Friends! Have a great day… see you tomorrow! :)

  21. Dear wonderopolis
    It is Owen from Mrs. Chevalier’s class I learned that the heart is not really shaped like a heart. Why is that? I think tomorrow’s is about vitamins or bingo because it says B-7 . You are amazing!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    • Dear Owen and Pooch– you both are amazing! Thanks so much for telling us about what you learned from today’s Wonder! It’s kind of curious that there are hearts of different shapes… but we aren’t certain about why that is. We did learn about the shape of the human heart– it looks like a fist! We think you’re very close with your Wonder guess… we’ll see what tomorrow’s Wonder will be! :)

  22. I really liked the video for this wonder! I thought that it was tring to teach us that everyone’s heart is different, in a similar way. I also thought it was a very creative way to show so many different kinds of hearts! My favorite kind of heart was the egg in the frying pan! :)

    • We’re so glad to hear that our heart Wonder made you smile, Happy Girl! Thanks for sharing your favorite part of the Wonder video– it sounds like you’re a creative Wonder Friend! We hope you learned something new and you’ll come back to Wonder with us again soon! :)

    • Thanks so much for sharing your enthusiastic comment, Maddy! We are glad to hear this Valentine’s Wonder made you smile! That was our goal! Have a SUPER day! :)

  23. This is our first attempt at posting to Wonderopolis. We are a grade 5/6 class of 54 with two teachers! We are working on non-fiction writing and think Wonderopolis will give our students authentic and engaging writing experiences. Thanks Wonderopolis!

    • Hello to our Wonder Friends in grades 5/6 in DetersMundy56! Welcome to Wonderopolis! We think it’s awesome that there are 56 people in your classroom! WOWZA! We look forward to WONDERing with you in the future– it sounds like you’re in the right place for an awesome and engaging learning experience! We always have fun here! :-)

    • We think so, too, Wonder Friend Tyson! We’re happy that you enjoyed our hearty Wonder! Did you learn anything new? :)

  24. I believe that we have half a heart. If you put two human hearts together it kind of looks like the hearts we see in stores.

    • What a great and creative idea, Sam! Thanks for sharing your awesome comment with us– our human hearts, put together, do resemble the hearts you see on Valentine’s Day! WAY TO GO! We’re so glad you visited us, we hope to see you again soon! :)

    • Hooray! We LOVE when our Wonder Friends connect– thank you for sharing your comment, Heather! Aren’t hearts super cool to Wonder about? :)

  25. Ok… let’s get this straight: the heart is not shaped as a heart that’s just what people think of it as it is actually shaped as a metaphorical shape.

  26. The heart is a a weird shape. It has holes everywhere and it is many other colors than red like some pink and white. I don’t want a real heart for Valentine’s Day at all!

    • Hey Wonder Friend Hi! The heart is a very different shape than the human heart- how crazy! The human heart keeps our body in check– it helps get blood to the rest of the body! We hope you receive some chocolate and a “Valentine’s Day” heart instead! :)

  27. This video was sweet. I cant wait for this next valentines day! Also there would be no world without love. It would just be too sad! I bet everyone would agree, that without love, there would be no man kind, am I right? Well I have to go cook breakfast, it was great wondering with you all!

    • Thanks so much, Mrs. Morris! We’re so glad you liked our Wonder about hearts! We couldn’t agree with you more – the world wouldn’t be as WONDERful as it is without love. However, there is always room for more!

      Thanks for making us smile and sharing your comment today! Have a WONDERful weekend! :)

  28. Hey Wonderopolis! I’m confused about why people think the human heart is a model to the candy heart… its nasty… but that is my opinion!

    • We agree with you, Taniyah. It is a little gross to think about. However, if you check out the third paragraph of the Wonder, it talks about how the human heart was just an inspiration for the heart shape. It also says that ancient philosophers may have just made it look better to us. That sounds a little bit better. What do you think?

      Thanks, for WONDERing with us today! :-)

    • Hi Austin! Check out the Wonder Gallery to see what a human heart looks like. We bet your heart would look something like it. Thanks for WONDERing with us! :-)

  29. I love your video. It was so cool. That is awesome. You did good. That was the best video I’ve ever seen. So, good job.

    • Thanks, Sydmeyu28! However, we can’t take credit for the video. It was shared online by a group called Moist Creation. We hope you enjoyed this Wonder and learned a lot of information about the heart! Thanks for WONDERing with us, Wonder Friend! :-)

    • Great questions, Random Person! We do our best to find videos and pictures that relate to each Wonder of the Day. However, we would love to add more user submitted pictures and videos to our Wonder Gallery. Thanks for WONDERing with us! :-)

    • You’re right, Alexis! We were hoping that the video would inspire you, and motivate you to read the Wonder Article. We hope you enjoyed the Wonder! :-)

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Have you ever wondered…

  • Is your heart shaped like a heart?
  • What is your heart made of?
  • How does your circulatory system work?

Wonder Gallery

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Try It Out

Do you have a lot of heart? Grab some loved ones and explore one or more of the heart-filled activities below:

  • Even if your heart isn’t shaped exactly like the hearts you see on valentines and bumper stickers, you can still show you have heart by making a special card for someone you care for. Think of someone who could use some cheering up and make them a card. It doesn’t have to be a Valentine’s Day card. It can be a “for no reason at all” card. Sometimes those are the best! Just tell the person what they mean to you. You never know when your heartfelt expression of caring will make someone’s day!
  • Think you know a lot about the heart and how your circulatory system works? Put yourself to the test then! Jump online and see if you can answer all the questions on the Cardiovascular System quiz correctly!
  • All this learning about the heart may have made you hungry. If so, why not make a heart-healthy snack or meal? Heart-healthy recipes include ingredients that doctors believe are good for your heart. Here are a few you can try at home:

Still Wondering

In Illuminations’ Every Beat of Your Heart lesson, children collect, organize and interpret data involving the heart rate at rest and after exercise.

Test Your Knowledge

Wonder What’s Next?

Tomorrow’s sweet Wonder of the Day is tasty and just might be good for you, too!

Upload a Photo or Paste the URL of a YouTube or SchoolTube Video.