Skeleton
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LearningTranscript
00:00Uh, sure, one sec.
00:10Hey, better safe than sorry with you.
00:17Dear Nat and Moby, my grandpa says I have a hard noggin, but doesn't everyone?
00:24Thanks, Joey.
00:26That's right, Joey.
00:27It's not just you.
00:29But sometimes it's still a good idea to give the old noggin a little extra protection.
00:34The human head is hard because of this bone, the skull.
00:39It's part of a framework of bones called the skeleton.
00:43Your skeleton supports and protects all your soft insides and helps you move around.
00:49Bones are made up of a bunch of different layers.
00:51On the outside is a thin membrane called the periosteum.
00:55It can be found all over every bone, except on the end points of long ones.
01:01Below that is a thick layer of hard, compact bone, which surrounds a layer of spongy bone.
01:09Bones aren't totally solid, though.
01:11In the center of most bones is a jelly-like substance called marrow.
01:16This stuff produces a lot of the body's blood cells.
01:20Bones also store calcium, which your body's nerves and muscle cells need.
01:26Well, that depends on age.
01:29People are born with more bones than they have later in life.
01:33As babies grow, some of their bones fuse together.
01:37Adults usually end up with 206 bones in total.
01:41Each one is adapted for a specific function.
01:45Like the breastplate, it's big and flat to protect your heart and lungs, whereas the
01:51small, delicate bones in our wrists and hands let us make precise movements.
01:56And our thick leg bones support our weight.
01:59Well, the spine isn't a single bone.
02:03It's made up of 33 little ring-shaped bones called vertebrae, stacked on top of each other.
02:10The spine is curved so that when you jump or take a step, it absorbs some of that impact.
02:16Vertebrae and other bones are connected to each other by tough tissues called ligaments.
02:22And bones are attached to muscles by similarly tough tissues called tendons.
02:27Without them, your skeleton would just, well, fall apart.
02:32At the ends of bones, there's a rubbery substance called cartilage.
02:37It's a kind of padding to protect against the wear and tear we get from moving around.
02:42The places where bones meet are called joints.
02:46Bones stretch across joints so your skeleton moves when the muscles expand and contract.
02:52And that's your skeleton, providing support, protection, and movement every day of your
02:58life.
02:59What do you mean that's a cheesy ending?
03:03Well, I don't see you talking.