Learn About the Human Body!

In honor of Valentine’s Day, we’re learning about the heart and other major organs!

First up, the human heart!


Curious about how your heart pumps blood? Use this model to learn about the right atrium and ventricle!

If you’ve ever squeezed your hand together to shoot pool water, you’re familiar with the basics of how your heart works. It’s a muscle that squeezes together to pump blood around your body! But shooting pool water with your hand is pretty messy and splashy. Your heart has to be a lot more orderly. In fact, because of how your body uses blood, your heart needs to pump blood in just one direction. Blood carries oxygen on it, and all the parts of your body need oxygen to work right. If the blood pumped backward, your body would get blood that had no oxygen in it!

In order to keep your blood flowing in the right direction, your heart has two pretty cool design features: chambers and valves. The chambers fill with blood, then squeeze tight to pump it out. Each side of your heart has an entry chamber called an atrium and an exit chamber called a ventricle (so your heart has four chambers total!). The entry and exit chambers pump one after the other to push your blood forward.

Each chamber also has an exit door called a valve. These keep blood from getting pumped backwards. When the ventricle contracts, the atrium’s exit valve closes so blood won’t push back into it. When the ventricle relaxes, its own exit valve closes to keep blood from spilling backwards into it. That way, the pumping of each chamber moves your blood forward!

Next, let’s explore how your lungs work!


What’s something you do all the time, all day and all night, without even thinking about it?Breathing! In fact, you breathe more than 23,000 times in just one day!

What organ is doing all that hard work? Your lungs! When you breathe in air, it travels to your lungs, which separate out the oxygen your body needs. Your lungs then send back everything you don’t need by breathing out. The oxygen is sent to your blood, where it’s used to make the energy you need to do everything, like running, eating, and talking.

How does it work? Under your lungs, a big muscle called the diaphragm is working hard to help you breathe! When you breathe in, your diaphragm moves down. This creates more room in your chest, which lets your lungs fill with air!

Your model lung works the same way, as you can see above. When you pull the balloon knot down, that creates more room in the bottle. This lets the balloon inside the bottle fill with air, just like your lungs do!

And last, but not least, muscles!


There are lots of muscles that help to move your arm in all the many ways it can move. The bicep and tricep muscles are two of the most noticeable, partly because of how big they get on some body builders. These paired muscles flex and extend the elbow joint, allowing you to bring a fork to your mouth or throw a frisbee. When one flexes, the other relaxes.

In this muscle machine, you’ll be mimicking the action of a muscle by pulling a string. This is actually pretty similar to how your muscles work. Muscles are made up of long fibers of cells, kind of like bundles of string. The cells in a relaxed muscle fiber are long and skinny. When a muscle flexes, the cells yank themselves together, going from long and skinny to short and round. This shortens the muscle fiber too, so anything the muscle fiber is attached to will move in the direction of its contraction. The string mirrors this by changing its length when you pull on it. Be sure to download the printable here.

Want to understand more about how your body works?

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