Meet the lungs | Respiratory system physiology | NCLEX-RN | Khan Academy

Let's say that this is you.

You're enjoying
a nice sunny day,

and you decided to take a
nice long, deep breath of air.

And of course, when
I say air, the part

that you probably
care the most about

is just the oxygen
part of that air.

That's the part that we,
as humans, need to survive.

So you take a deep
breath, and let's say

that you take it
through your mouth.

You take a deep breath
through your mouth.

And then let's say you
take one more deep breath,

a second deep breath.

And you take that one
through your nose.

Now you might think, well, these
are two totally different ways

of getting in air.

That's certainly
how it looks when

you look at a mouth and a nose.

It doesn't look like
they have much in common.

But the truth is that actually.

If you follow the air, it almost
follows an identical path.

So the air is going to go
into the back of the throat,

really regardless of
how you took it in.

So here we have air
coming in from the nose.

And here you have air
coming in from the mouth.

And they meet up in
the back of the throat.

And then they go
down, down, down.

They go towards this thing
that we call the Adam's apple.

I'm going to bring up a
little bit of the canvas

so you can see it more easily.

But basically, you see this
Adam's apple right here.

And actually you can
go ahead and take

a feel of your own Adam's apple.

It's a pretty cool structure
in the middle of your throat,

and everybody has it.

That's the first
thing I want to tell

you is that everybody
has it, not just men.

Women have it too.

And the reason it's
called an Adam's apple,

it's called an Adam's apple
because Adam is generally

a boy's name.

And so it's to remind us
that usually men or boys have

larger Adam's apples than girls.

And if you're trying to find it,
I just also want to point out

there's this notch here.

And if you can feel the
notch with your fingers,

that gives you a nice clue
as to where it's located.

But this is it.

This is the Adam's apple.

And what it does is it helps
you control your voice.

And actually, another name for
the Adam's apple, sometimes

people call it the voice box.

The voice box.

And of course, air is passing
through the voice box,

and it's kind of the
entryway into the trachea.

And so it actually
allows me to (FALSETTO)

make my voice really
high, (DEEP BARITONE)

or make my voice
very low, depending

on how you change the muscles
around in that Adam's apple.

So that's actually the
kind of first cool thing

I want to point out to you
is that you can actually

control your voice.

I'm sure you knew this
already, but what you're using

is your Adam's apple,
or your voice box.

Now air keeps going.

Air is just going to keep
making its journey down--

and specifically, of
course, the part of air

I said we care
about is the oxygen.

It's going to keep
making its journey down

into the lung area.

So this is now the lung area.

It's going down the trachea,
and it goes into the two lungs--

the right and left lung.

This is the left lung.

I'm going to put L for left.

And this is the right lung.

I'll put R for right.

And immediately you're
thinking, well, wait a second,

aren't they switched?

I want you to
remember that this is

from the perspective of the
person who owns the lungs,

so that's why I'm putting
left where I put it

and right where I put it.

Now we should probably
go ahead and start

labeling some of this.

You can see that the lungs
actually don't look identical.

They look slightly different.

For example, this
one has three lobes.

The right side has three lobes.

We call it the upper lobe,
middle lobe and lower lobe.

And the left one
only has two lobes.

So that's the first
kind of big difference.

And the other difference
is that you actually

have this thing in the middle
that we call a cardiac notch.

This thing right here, this
is called the cardiac notch.

And the reason we
call it that is

that it's a little
spot that gets

formed because the
heart is literally

kind of peeking out here.

And as a result, it
kind of makes a notch

in the lungs when it develops.

So the heart takes up a
little bit of space here.

This is our heart.

And as a result, it
makes that notch.

So this is our heart space here.

So on the other
side, you've got,

of course, your two lobes--
your upper and lower lobe.

And these are two clues, so if
you ever see a lung just kind

of sitting by itself and
you want to figure out

whether it's the left
lung or the right lung,

you can look for
the number of lobes,

or you can look for
that cardiac notch.

Now around these
lungs, you've got ribs.

So you've got ribs here,
and between the ribs,

you've got rib muscles.

And they are, of
course, on both sides.

And below the lungs
and below the heart,

you've got a big muscle.

Actually it's going
to come through here.

I'm going to just kind of
go through the word heart.

And it basically
becomes the floor.

So the heart and
the two lungs, they

sit on this floor made
up of this muscle.

And this muscle is
the diaphragm muscle.

So this diaphragm muscle
makes up the floor.

The ribs make up the walls.

So what do we have?

We have basically a room.

We have a giant room
with walls and a floor.

And this entire room we
actually call the thorax.

So within this room then,
you have your two lungs

and your heart.

So far, so good.

But I haven't done a very nice
job of actually showing you

where the air goes.

I've just kind of pointed that
it goes through the two lungs,

but you don't actually get to
see where it goes after that.

So I'm going to
erase a lot of this.

I'm going to reveal
to you what it

would look like if you could
slip on some X-ray glasses

and look at your two lungs.

This is kind of what
it would look like.

You've got all this
interesting architecture.

And the easiest way to
think about this, probably

the simplest way to think about
this, is to imagine a tree.

So imagine a tree, and that tree
has been flipped upside down.

So you've got all these
branches off that tree.

And they're branching
and branching.

And if you flip this
tree upside down,

you start seeing that
it looks a lot like what

we have in our lungs.

Our lungs basically look like
a flipped upside down tree.

And we even call it that.

We even call this
entire structure,

we call it a bronchial tree.

So when you look at
the lungs and they

look kind of messy
or complicated,

just think of them as an upside
down bronchial tree, and all

of a sudden it'll
look much simpler.

Basically in the middle,
you've got this nice trunk.

Right?

This is our trunk.

And then it starts kind
of branching from there.

So air goes down this main
trunk, this trachea, and then

it kind of starts splitting up.

And each of these colored
regions-- the green region

or the purple region--
serves a different lobe.

So this green region serves
the lower lobe down here.

The purple serves
the upper lobe.

And on this side, you've got
an upper, a middle, and a lower

lobe.

Now I know it looks a little
bit strange, because you've

got some green branches in
what should be the middle lobe,

like right here.

You've got some orange
branches in what

looks like the upper
lobe, like right there.

But what you have to
remember-- and this

is kind of tricky
to do and just try

to play with it
in your head-- is

that what you have is basically
a three-dimensional lung.

So you have to imagine
that we are only

looking at it from
the front side.

But, of course, that
middle lobe does go back.

And if it went back, then
you'd make perfect sense

of why the orange branches
are where they're at.

Now let me continue
the air journey,

because I want to make
sure we finish it off.

So let's say we take a little
branch like this, we expand it.

We keep zooming into
it, zooming into it,

zooming into until
it's microscopic.

You can't see it with
your eyes anymore,

but you could see it
under a microscope.

It would look like this.

It would basically,
under a microscope,

look like a bunch of
little sacs like this.

And these sacs, we
call these alveoli.

Alveoli.

And the air actually kind
of runs into the alveoli.

It has a dead end, and
then it comes back around.

And then you breathe it out.

So that's how breathing works.

The air goes all the way
in through your mouth, down

to the alveoli, takes a
U-turn, and then goes back out.

But before it does
that, before it leaves,

very close to the
alveoli is blood.

And let's say blood is coming
this way and going that way.

And what will happen is
that actually into the blood

will go oxygen.

Oxygen will actually
go into the blood.

And out of the
blood will be waste.

So you'll have some
carbon dioxide waste

that your cells
have been making.

And that waste
actually then gets

thrown back into the alveoli.

So now you can see how oxygen
gets from the outside world,

gets breathed in through
the lungs when you inhale,

gets down into the alveoli,
exchanges with the blood,

and then you exhale and let
all that carbon dioxide out.