[Intro plays]

Jessi: believe it or not, there's something a lot like this inside of you and inside of me, too. It's a skeleton! You may have seen skeletons, like the ones they have of dinosaurs in a museum or maybe plastic models of human skeletons, like this, maybe you've even seen dancing skeletons around Halloween, but do you know how important, cool, and powerful your skeleton really is?

Let's get to know your bones, from how they help you move to the different kinds you have and the super special job they have to do. Let's get started.

One of your skeleton's important jobs is of course to hold your body up. Your muscles are strong, but they need a frame, something to hold on to. Without a skeleton, you'd be all loosey goosey, and you wouldn't be shaped like you. And it goes both ways, without your muscles, your skeleton would just be a pile of bones, it's only by squeezing and relaxing your muscles that you're able to move your bones. So that silly dancing Halloween skeleton is just pretend, because it doesn't have muscles.

So your bones are hard enough to hold the weight of the rest of your body, but they're also hard enough to act like a protective shield around your soft, squishy organs. Your ribs, for example, are bones that protect your lungs and heart, so that even if you get a big strong bear hug, your insides don't get squeezed, too.

And speaking of strong, the strongest bone in your body is also the biggest, longest and heaviest bone you have. It's the bone that goes from your hip to your knee, called the femur, and that bone has to be big and strong because when you run, jump, walk, or even just stand still, a lot of the weight of your body falls on your femurs.

Now where do you think your smallest bone might be? The very smallest bone you have is actually in your ear. This little bone called the stapes looks kind of like a stirrup. Even in adults, it's only about the size of a grain of rice. But this tiny bone has a big job. When sounds enter your ear, they make this little bone move back and forth, these vibrations are what your ear picks up as sound. So without this teeny tiny bone, you wouldn't be able to hear.

Now I have a question: how many bones do you think we have? Well, it kinda depends. It sounds crazy, but you have fewer bones now than when you were born. Newborn babies have about 300 bones, but by the time you've finished growing, you'll only have 206. So where did all those extra bones go? Nowhere! As babies grow, some of their bones grow together, or fuse into one bigger bone, for example, your skull.

Your hard noggin is actually 21 bones fused together, plus one that's always separate, your jaw. Your skull starts out as a bunch of separate bones because that leaves lots of room for your brain to get bigger. And once you're fully grown, the fused parts make an incredibly strong shield to protect your precious brain.

One final fun fact about your skeleton: your bones are alive. Even though we often thing of skeletons as not living, like the ones we see in museums or models, your bones are full of living cells. Some of these cells are what make your bones grow and repair them if they get hurt, and other cells, which are tucked away in the thick spongy layer deep inside your bones, have a very special job. They make your blood. That's right, most of the stuff that's in your blood is actually made inside your bones. It's because your bones are alive that they're able to grow, like they're doing in you right now, and they won't be done until you're about 25 years old. But even then your bones will still be busy holding you up, helping you hear, and making your blood.

So bones in museums are cool, and Halloween skeletons are fun don't get me wrong, but nothing's more scary powerful than your own living skeleton and all the great stuff it does for you.

Do you have a question about animals with big bones, small bones, or no bones at all? Just let us know by getting help from an adult and leaving a comment below or emailing us at kids@thescishow.com, and we'll see you next time.