- [Voiceover] In this picture we've got a pregnant mom
and a little fetus inside of her uterus.
That's the name of this little chamber
that the fetus is hanging out in.
This uterus is an organ and
women have this organ.
It's a very, very strong organ, very muscular organ.
In fact, if you've ever gone to a delivery
and you've heard people chant, "Push, push, push,"
they're literally kind of encouraging mom
to push down on this uterus
and help the baby come out into the world.
So this uterus is the room in which the baby lives.
But the environment in which the baby lives
is actually very different as well
from how we live outside, in the sense that
there's amniotic fluid in this space, right,
and the baby is actually swimming in this fluid,
for months at a time.
For nine months, baby is swimming in amniotic fluid
and that brings up some obvious questions.
How is baby able to breathe or eat?
How does it take care of its needs?
Let's think about what those needs are.
Let's enumerate them.
One of them is oxygen.
How does a baby take in oxygen
if it's not getting it from the lungs?
The lungs are actually full of amniotic fluid, by the way.
How is it able to get nutrients?
Things like sugar, glucose,
that it needs for energy.
I'll put example, glucose.
Let's think about waste.
How does it get rid of things like carbon dioxide?
For us, it's very easy,
we just kind of exhale
or take a breath out.
But how does a baby do that if I just said
that the lungs are full of fluid?
How does it get rid of waste products like carbon dioxide?
It turns out all of these kind of issues
are obviously very important,
and the mom and the baby work together a solution.
This is the first
chance for mom and baby
to really work together on something.
The solution is something called the placenta.
You may have heard of the placenta.
The baby actually sends a couple
of vessels up to the placenta.
These are little umbilical arteries.
It also sends up an umbilical vein to the placenta.
The vein brings blood back from the placenta.
In all these vessels,
all three of these,
make what we call the umbilical cord.
You may have heard of the umbilical cord
and now you know what's inside of it.
The umbilical cord actually, if you were to cut it,
I'm gonna show you what it would look like
if you were to cut across it.
It's actually an easy thing to remember
because it has
a big, floppy little vessel right here.
That's the umbilical vein.
It's got oxygen,
that's why I'm drawing it as red
even though it's a vein
because it's coming back to the heart,
that's why we call it a vein.
And you've got umbilical arteries.
These two actually don't have too much oxygen.
That's why I'm drawing them in blue,
just to show that they're low in oxygen.
They're called umbilical arteries
because they're going away from the heart.
The umbilical arteries and the umbilical vein
look like this, actually they're kind of
they're not just freely floating out there.
They're actually encased in this jelly,
and the jelly is called Wharton's jelly.
I'm actually just gonna redraw this,
just to show you how I remember this.
Sometimes it' hard to remember
if there's one artery or two arteries.
I think of the mouth
as a vein, or a V.
And I think of the eyes as two little A's.
That's my little trick for remembering
that there are two umbilical arteries
and one umbilical vein,
and that they're all encased in the Wharton's jelly,
and this is the umbilical cord.
This is the overall picture,
now I wanna go into some detail
to really get us to understand how the placenta works
because it honestly is one
of the most interesting organs
in the sense that it allows us to do things
that we simply cannot do today,
but we could do for many, many months at a time.
I'm gonna invert the way that I drew this.
I drew this one way above
and I think you'll see how I flipped it around here.
This'll be the uterine wall.
Again, remember the uterine wall
is a nice, strong, muscular wall.
Let me label it so it's clear.
This is uterine,
I'll just call it uterus,
the wall of the uterus anyway.
On the insides you've got,
actually I'm working from the outside in.
Let me draw some of mom's blood vessels.
She's got some blood vessels
coming up like this, this is a little uterine artery.
This, of course, gives oxygen to the uterus.
We said it's a big muscle
so it definitely needs blood vessels,
like arteries and veins.
I'll draw a couple of them.
I'll draw another uterine artery over here,
and I'll draw one third one over here.
Of course, they are many more than three
but I just wanna give you the concept
that there are some uterine arteries.
There are also some uterine veins.
Let me draw some uterine veins as well.
I'll draw one over here.
These blue ones are the uterine veins,
I'll label this one over here.
What they're doing is they're actually
going through a layer of tissue.
Let me draw in a layer of tissue for you
so you see exactly what I mean.
There's a layer of tissue here,
they're going through it.
This layer of tissue is mom's tissue.
I'm gonna label it mom's tissue,
or I'll just call it mom's.
It looks a little bit, you have to stretch your imagination,
but it looks a little bit like a plate.
This entire thing that I'm shading in in red
is one of the parts of the placenta.
So we've already started drawing the placenta.
Actually, let me switch colors.
This part is known as the basel plate.
If you're talking about the basel plate
you're talking about this bit of tissue here,
with the blood vessels, the uterine arteries,
and the uterine veins.
Just to be clear, it belongs to mom.
This is mom's cells.
Now we get into some really fun stuff.
All these uterine arteries,
they squirt out blood.
They don't go into any other vessel.
They just squirt out blood into an open area.
Let's say there's a red blood cell here,
this red blood cell literally
could touch, physically touch
a red blood cell over here.
They literally could
come up, and meet,
and maybe shake hands.
They could then go down the veins.
This is really, really different
from how we usually think about blood cells
traveling always within a vessel.
Cuz here it's kind of a pool.
You have this circulation that happens
because you have these red blood cells,
as I've drawn them,
kind of going up, into the middle,
then circulating into the veins.
You have this interesting circulation
where you basically have blood coming up
through the arteries and down into the veins.
The way I think about this,
and you can maybe choose
your own kind of analogy.
But for me, I think of it a little bit like a hot tub.
The uterine arteries are like the jets of water,
coming up.
The uterine veins are literally
like the drains in the hot tub.
It becomes almost like a swirling pool of red blood cells.
Importantly, these red blood cells have with them
oxygen, they have nutrients,
so they have a lot of the stuff that our fetus
is interested in getting access to.
Let's switch gears, let's think about our fetus.
Our fetus has got, we said a couple
of umbilical arteries coming down.
I also said that they're coming down
inside of this Wharton's jelly,
this umbilical cord of Wharton's jelly.
Actually what happens is that the vessels
actually branch out and they split up.
The uterine arteries,
form lots and lots and lots of little branches.
I'm gonna draw them in for you.
Let's say that the branches go all over the place.
They go like this.
Let's draw five or six branches over here.
Let's draw some branches down on this side too.
We've got lots of branches off the uterine arteries.
They want access to the oxygen and nutrients.
Guess what they do?
They just kind of push in, in fact,
you have little cells here.
I'm gonna draw some pushing in right here.
You got little cells that I'm drawing
in white, called trophoblast.
They literally do this.
They just kind of push in.
These white cells are trophoblast cells.
They're good at invading.
You could think of them as invading
or if you wanna be less aggressive,
you could think of them as being just curious.
These little fetus cells, called trophoblasts,
start pushing in.
And within the trophoblast is a little blood vessel.
This blood vessel now
is in very close contact
with mom's red blood cells,
you've got red blood cells coming up
alongside of it.
Now what's gonna happen through diffusion,
is that oxygen is gonna go into the fetus' blood cells.
So oxygen is going this way,
as well as nutrients.
Oxygen, nutrients go inside,
then you have carbon dioxide leaving.
So carbon dioxide actually goes
into the pool of blood.
It's a really, really cool thing
that the red blood cells aren't touching,
the mom's red blood cells
are not touching baby's red blood cells
cuz, of course, baby's red blood cells
are within blood vessels,
these are within blood vessels.
These things right here are not open,
they're closed vessels.
Once that exchange happens,
they continue to stay closed,
and you get a little capillary coming back.
You've got capillaries coming back
from every part of this.
All of these have been doing the same thing.
Going inside of this pool of blood.
It actually gets a little bit more complicated
than the way I've drawn it, in fact,
a more accurate drawing might be with more branching.
You might have something like this,
where it really has lots of surface area.
It comes back around,
and you have the blue vessels
going into each one
of these finger-like projections.
You have a lot of gas exchange happening.
This would be maybe a better way of drawing it
but the concept is the same.
You basically have all this
wonderful diffusion happening.
As a result you actually have
nice, rich oxygenated blood
returning to the baby.
This is finally allowing the baby to have access
to oxygen and nutrients
and get rid of its waste, its carbon dioxide.
Each one of these is actually doing the same thing
with red or oxygenated blood coming back.
Instead of having two vessels,
it all dumps into one vessel down the middle.
This vessel, as we already know,
is called the umbilical vein.
This is actually the umbilical vein.
If we call the bottom one the basel plate,
then, of course, you're guessing that
there must be some name for this.
This, of course, has its name
called the chorionic plate.
This one, you can already tell,
this has all the cells from the fetus,
so this belongs to the fetus.
You've got some tissue that belongs to the fetus,
that would be the chorionic plate and all of its contents.
You've got some tissue that belongs to mom,
that's the basel plate.
Then you've got some
shared tissue, or space, in here.
All these little projections belong to the baby.
But the actual pool,
this pool of blood that's circulating.
That pool of blood belongs to mom.
So really, the placenta is a combination
of all of these things.
I think of the placenta then
as the first time that mom and baby
work together for a common purpose.