Hey smart people.
A couple of months ago, our son got his very first tooth.
And then for like 3 months, he still only had one tooth.
He looked adorable.
But also a little bit ridiculous.
Now this got me thinking… where do teetheven come from.
Like…how does that happen?
How do bones start growing out of our faces? So,
I did some research, and what I found…
I’ll never be able to unsee.
And you probably won’t be able to unseeit either.
Let’s check it out!
Teeth are weird and awesome, and they grow in weird and awesome ways.
So where do they come from?
To understand that, we have to go way back.
Before you were even born.
Actually before you even had a brain… no.
I mean when you looked roughly like this.
Around three weeks into development, your body was just a flat little disc.
You were pretty two-dimensional.
Then you rolled yourself up into a tube.
It’s one of the most important things you’veever done!
So congrats on that.
The tube that forms
from this embryonic origami is surrounded by incredibly important stem cells.
They migrate and build some of your most important parts – the spinal cord, brain,
脊髓 大脑 骨头
in your middle ear to parts of your heart… and your teeth.
About 6 to 8 ___ weeks in,
little groups of these cells form bumps under what will become
your gums, and they undergo a transformation!
Some become odontoblasts – these cells make dentin,
the tough, fibrous core of the tooth.
But the cells on top of those bumps transform too,
into ameloblasts, the cells that build enamel,
the hard outside layer of your teeth.
The process of building enamel is some awesome cellular nanotechnology,
up in your face.
Enamel-building cells secrete a mixture of chemicals that hardens into mineral crystals.
The cell moves up,
and secretes more mineral on top of the last layer.
Eventually the enamel-building cell dies off, leaving a long crystalline rod behind.
Millions of these rods packed together make up the enamel layer of your teeth.
This mineral is mostly hydroxyapatite – tough stuff
that’s rich in calcium and phosphate.
Basically rocks, in your mouth.
And like rocks, they can last a really long time
under the right conditions.
Would you believe thirty thousand years?
with Matt Brown he’s the Director of the Texas Vertebrate
What is that enormous thing right there?
This giant tooth right here is the canine tooth
of a saber-toothed cat from an animal
What’s often called a saber-toothed tiger.
We’re looking at this individual tooth that’s fallen out of the skull.
When we look at a
fossil like a regular bone other minerals have taken the place
of that bone and it’s
sort of rock but this is pretty much enameled
like the tooth the way that that cat grew it.
Yeah, what I’m holding here
in my hand is pretty much what was walking around inside
of the living Smilodon.
Got anymore old teeth for us to look at?
We sure do, we’ve got probably about a millionof them.
So these are teeth from mastodons and you can see
that these teeth here they look pretty
familiar as teeth they look very similar to to even some of our molars.
This tooth here has a giant cavity in it just
like my teeth we have got you can see
the same thing in the fossil record.
It’s a reminder that these animals were aliveand walking around.
And the mastodon didn’t brush their teeth.
That’s probably the case.
I bet we can go even older.
This is part of the left side of the face
of a Tyrannosaurus and we’re looking at
teeth here preserved in this skull that are
about 70 million years old that tooth is not
messing around but very clean much
better dental health and they may have been brushing
or maybe a meat diet is better for less cavities.
I bet we can go even older.
We sure can.
We’re standing in front of a cabinet from the Jurassic period.
This is about a
hundred ninety five million year old dinosaur called Dilophosaurus and we’re
looking at the enamel again. All right
You got anything older? We do. So our last
stop is this cabinet here in the Pennsylvanian some of
the oldest teeth that we have in this building with
about 2 million fossils in it and so we’re
looking at a 300 million year old tooth
with enamel that would be very very
similar to the enamel that was swimming around in this animals mouth.
That is some long lasting teeth 300 million
years old and that’s unmistakably a
shark tooth. That’d make a killer necklace.
So building enamel is like making rocks inyour mouth.
When all this enamel nano-fabrication is complete, your baby teeth finally bust out.
And they each leave behind an empty space.
And it’s here, thanks to stem cells,
that the same tooth-growing process repeats to
form your permanent teeth. So,
your baby teeth started growing even beforeyou were born.
And by the time your baby teeth came in,
your permanent teeth were already growing in behind
That means at one point your skull lookedlike this!
Yeah… it’s pure nightmare fuel.
Told you you wouldn’t be able to unsee it.
As your baby teeth feel those adult teeth growing
in behind them, their root dissolves
and they fall out.
Eventually you get between 28 and 32 teeth in your adult mouth.
But after those adult teeth grow in,
all the stem cells that laid down the crystal nanorods self-destruct,
so that’s the only set ofreplacement teeth you get.
But why don’t we keep our teeth-growingstem cells?
Scientists aren’t totally sure yet.
But maybe one day they could figure out a way to grow new teeth,
and turn us into human
On second thought, maybe not.
Brushing and flossing is much less frightening.
So that’s how teeth grow.
Before you even had a brain,
a special army of cells crawled to your head, and set up
nano-crystal factories to basically buildrocks inside your skull.
I think someone should tell the Tooth Fairy
that THAT story is worth more than a dollar.