1 00:00:02,220 --> 00:00:17,219 Believe it or not, there's something a lot like this inside of you and inside of me, 2 00:00:17,219 --> 00:00:18,219 too. 3 00:00:18,219 --> 00:00:19,219 It's a skeleton! 4 00:00:19,219 --> 00:00:22,719 You may have seen skeletons, like the ones they have of dinosaurs in a museum, or maybe 5 00:00:22,719 --> 00:00:25,980 plastic models of human skeletons, like this. 6 00:00:25,980 --> 00:00:29,960 Maybe you've even seen dancing skeletons around Halloween! 7 00:00:29,960 --> 00:00:34,560 But do you know how important, cool, and powerful your skeleton really is? 8 00:00:34,560 --> 00:00:38,579 Let's get to know your bones, from how they help you move, to the different kinds you 9 00:00:38,579 --> 00:00:41,079 have and the super-special job they have to do. 10 00:00:41,079 --> 00:00:42,280 Let's get started! 11 00:00:42,280 --> 00:00:46,020 One of your skeleton's important jobs is, of course, to hold your body up. 12 00:00:46,020 --> 00:00:50,240 Your muscles are strong, but they need a frame, something to hold onto. 13 00:00:50,240 --> 00:00:54,340 Without a skeleton, you'd be all loosey-goosey, and you wouldn't be shaped like you. 14 00:00:54,340 --> 00:00:55,939 And it goes both ways. 15 00:00:55,939 --> 00:00:58,840 Without your muscles, your skeleton would just be a pile of bones. 16 00:00:58,840 --> 00:01:03,079 It's only by squeezing and relaxing your muscles that you're able to move your bones. 17 00:01:03,079 --> 00:01:05,120 So that silly dancing Halloween skeleton? 18 00:01:05,120 --> 00:01:07,519 It's just pretend, because it doesn't have muscles. 19 00:01:07,519 --> 00:01:11,719 So your bones are hard enough to hold the weight of the rest of your body, but they're 20 00:01:11,719 --> 00:01:16,459 also hard enough to act like a protective shield around your soft, squishy organs. 21 00:01:16,459 --> 00:01:20,739 Your ribs, for example, are bones that protect your lungs and heart, so that even if you 22 00:01:20,739 --> 00:01:24,620 get a big, strong bear hug, your insides don't get squeezed, too. 23 00:01:24,620 --> 00:01:29,280 And speaking of strong, the strongest bone in your body is also the biggest, longest, 24 00:01:29,280 --> 00:01:30,560 and heaviest bone you have. 25 00:01:30,560 --> 00:01:33,859 It's the bone that goes from your hip to your knee, called the femur. 26 00:01:33,859 --> 00:01:38,959 And that bone has to be big and strong, because when you run, jump, walk, or even just stand 27 00:01:38,959 --> 00:01:41,859 still, a lot of the weight of your body falls on your femurs. 28 00:01:41,859 --> 00:01:45,219 Now, where do you think your smallest bone might be? 29 00:01:45,219 --> 00:01:49,159 The very smallest bone you have is actually in your ear! 30 00:01:49,159 --> 00:01:52,980 This little bone, called the stapes, looks kind of like a stirrup. 31 00:01:52,980 --> 00:01:56,540 Even in adults, it's only about the size of a grain of rice. 32 00:01:56,540 --> 00:01:59,280 But this tiny bone has a big job. 33 00:01:59,280 --> 00:02:03,079 When sounds enter your ear, they make this little bone move back and forth. 34 00:02:03,079 --> 00:02:06,060 These vibrations are what your ears pick up as sound. 35 00:02:06,060 --> 00:02:09,340 So without this teeny tiny bone, you wouldn't be able to hear. 36 00:02:09,340 --> 00:02:10,919 Now, I have a question. 37 00:02:10,919 --> 00:02:12,740 How many bones do you think we have? 38 00:02:12,740 --> 00:02:14,460 Well, it kinda depends. 39 00:02:14,460 --> 00:02:18,560 It sounds crazy, but you have fewer bones now than when you were born. 40 00:02:18,560 --> 00:02:21,879 Newborn babies have about 300 bones! 41 00:02:21,879 --> 00:02:25,439 But by the time you're finished growing, you'll only have 206. 42 00:02:25,439 --> 00:02:27,699 So where did all those extra bones go? 43 00:02:27,699 --> 00:02:28,699 Nowhere! 44 00:02:28,699 --> 00:02:33,759 As babies grow, some of their bones grow together, or fuse into one bigger bone. 45 00:02:33,759 --> 00:02:35,500 For example, your skull. 46 00:02:35,500 --> 00:02:40,659 Your hard noggin is actually 21 bones that are fused together, plus one bone that's 47 00:02:40,659 --> 00:02:42,539 always separate — your jaw. 48 00:02:42,539 --> 00:02:46,819 Your skull starts out as a bunch of separate bones, because that leaves lots of room for 49 00:02:46,819 --> 00:02:48,180 your brain to get bigger. 50 00:02:48,180 --> 00:02:52,960 And once you're fully grown, the fused parts make an incredibly strong shield to protect 51 00:02:52,960 --> 00:02:54,259 your precious brain. 52 00:02:54,259 --> 00:02:58,539 One final fun fact about your skeleton — your bones are alive! 53 00:02:58,539 --> 00:03:02,340 Even though we often think of skeletons as not living, like the ones we see in museums 54 00:03:02,340 --> 00:03:06,020 or models, your bones are full of living cells. 55 00:03:06,020 --> 00:03:10,240 Some of these cells are what make your bones grow, and repair them if they get hurt. 56 00:03:10,240 --> 00:03:14,819 And other cells, which are tucked away in the thick, spongy layer deep inside your bones, 57 00:03:14,819 --> 00:03:16,340 have a very special job. 58 00:03:16,340 --> 00:03:17,879 They make your blood. 59 00:03:17,879 --> 00:03:18,879 That's right! 60 00:03:18,879 --> 00:03:23,099 Most of the stuff that's in your blood is actually made inside your bones. 61 00:03:23,099 --> 00:03:27,580 It's because your bones are alive that they're able to grow, like they're doing in you 62 00:03:27,580 --> 00:03:28,659 right now. 63 00:03:28,659 --> 00:03:31,280 And they won't be done until you're about 25 years old. 64 00:03:31,280 --> 00:03:35,740 But even then, your bones will still be busy holding you up, helping you hear, and making 65 00:03:35,740 --> 00:03:36,740 your blood. 66 00:03:36,740 --> 00:03:40,379 So bones in museums are cool, and Halloween skeletons are fun, don't get me wrong. 67 00:03:40,379 --> 00:03:45,560 But nothing's more scary-powerful than your own living skeleton and all the great stuff 68 00:03:45,560 --> 00:03:46,560 it does for you. 69 00:03:46,560 --> 00:03:51,360 Do you have a question about animals with big bones, small bones, or no bones at all? 70 00:03:51,360 --> 00:03:55,219 Just let us know by getting help from an adult and leaving a comment below, or emailing us 71 00:03:55,219 --> 00:03:57,560 at kids at the scishow dot com, and we'll see you next time!