00:01
Now, we're going to talk about
the respiratory system,
whose goal ultimately is to achieve
gas exchange with the blood.
00:08
But there are many important
structures that move and modify air
before it gets to that point.
00:14
So we're going to start
by talking about
the structure and function
of the nasal cavity
before moving a little bit deeper
down to talk about the larynx.
00:23
Then once we get into
the chest cavity,
we're going to be talking
about the trachea, bronchi,
something called the hilum
and the major blood vessels
that supply the lung.
00:31
We're going to talk about
the wrappings of the lung
and the chest cavity
called the pleura.
00:37
We're going to talk about
superficial anatomy of the lungs,
as well as bony thorax
that encases the lungs.
00:44
And then finally,
we're going to talk about
the major muscle of respiration,
which is the diaphragm
and the nerve that innervates
it, which is the phrenic nerve.
00:53
The respiratory tract itself
can be divided into
an upper and lower portion.
00:59
The upper portion consists of nasal
sinuses, nose, the nasal cavity,
a shared oral, digestive,
and respiratory space
called the pharynx.
And then the larynx.
01:11
After which,
we have the lower respiratory tract
starting with the trachea
that divides into bronchi
to supply the lungs.
01:20
We're going to focus first on
the upper respiratory tract.
01:24
In particular, we're going to start
with the nose and nasal cavity.
01:28
And this anterior view of a skull,
we see that the anterior
most portion of the nose
isn't actually made up of bone,
but it's made up of cartilage
what makes it very flexible
and very movable.
01:40
Further back, we do have bone that's
connected to the rest of the skull.
01:46
If we were to take
off that cartilage,
and look into the
nasal cavity itself,
we see that there's a wall
at this point made up of bone
called the septum
that divides the cavity into
left and right cavities.
02:02
We also noticed that laterally
on each nasal cavity wall,
we have these weird shaped bones
called nasal cancha, or turbinates,
that have that shape to help achieve
their very important functions.
02:16
Now let's look at a sagittal
view right down the midline.
02:20
And we're going to look towards
the septum from the left side.
02:25
Anteriorly,
it's again made up of cartilage,
which gives it the flexibility
that you're probably familiar
with the external nose.
02:33
But further back,
it's made up a bone so it's rigid.
02:39
Now, if we were to
take a coronal section,
somewhere around this bony septum,
we see there's actually
a lot of spaces here.
02:48
So we again find the bony
septum in the midline,
separating the cavity
into left and right.
02:54
And we again see these
weird shaped bones
coming off of the lateral wall,
the cancha or turbinates,
and we see that they're
named for their location.
03:04
We have a superior, a middle,
and an inferior nasal chancha
on either side.
03:11
We also noticed surrounding
the nasal cavity,
the spaces within the bone
called sinuses.
03:18
and they're lined
by mucous membranes
that are made up of the
same type of epithelium
as the rest of the nasal cavity.
03:25
And their function
is somewhat unknown.
03:29
We don't really know there
are a lot of theories.
03:31
For example, these spaces
helped make the head lighter.
03:35
They add resonance to the voice.
03:39
Regardless of what they're
really doing there,
they are important because they are
connected to these nasal cavities.
03:46
And therefore, infections,
for example, can spread into them
and cause inflammation
or sinusitis.
03:55
Let's go back to this
midline sagittal view
where we again see
the nasal septum.
04:00
This time in pink because we've
covered it with some mucosa.
04:05
If we were to take away that septum
by moving just a little bit
to the right of midline.
04:13
And again, taking it from
this view from the left,
we will now see the right
lateral wall of the nasal cavity.
04:22
Now, we can see these
conquer or turbulence.
04:26
We see the superior, the middle, and
the inferior nasal turbinates here.
04:34
And there's a lot of
functions to these turbinates.
04:37
For example, the air we
breathe in is fairly dirty,
It's fairly dry and it's fairly cold
compared to the rest of the body.
04:43
And they actually create turbulence
in conjunction with the
mucosa that lines these
helps to warm the air,
humidify it, and help clean it.
04:55
It also helps to direct air upwards
to the top of the nasal cavity,
where we have a special type
of mucosa called olfactory mucosa.
05:05
And olfactory means smelling.
05:07
So this area is a
specialized area for smell.
05:11
And in fact, in this area,
there are a bunch of tiny
nerves that collectively make up
the first cranial nerve
or olfactory nerve,
which is the nerve of smelling.
05:22
And these tiny little nerves
pass through the school at this area
to reach the cranial cavity
at a special spot called
the olfactory bulb,
which will then have attracted
that goes back to the brain
to process the sense of smell.
05:37
Let's look at a bit of
a complicated issue here
when we talk about
breathing and eating.
05:44
So we just talked about air
moving through the nasal cavities,
and its objective is to ultimately
get down into the lungs.
05:53
However,
we also have an oral cavity
through which things like
food and water going to pass.
05:59
Eventually, back to the
esophagus into the stomach.
06:03
But this creates a problem
because as you can see,
there's a space where both food
and water are shared with air.
06:10
And so how do we prevent
things like food and water
from ending up in the lungs
and essentially choking us.
06:19
So let's look what happens
when we try to swallow
a portion of food.
06:26
When we've chewed up a bit of food,
it formed something called a bolus.
06:30
And it's held in place
here by the tongue.
06:34
If we look posterior to this,
we see that there's an area
of the palate that lacks bone.
06:41
And that's the soft palate.
06:43
And more inferiorly at
the base of the tongue,
we have this little flap of
tissue called the epiglottis.
06:51
During the act of swallowing,
the tongue and several other muscles
push this bolus back posteriorly.
06:59
And the soft palate acts
as a flap to prevent food
from going up into
the nasal cavity.
07:04
While the epiglottis,
serves to flap down and protect
the opening to the airway
as food is being swallowed.
07:13
Therefore,
it forces food posteriorly
and back into the
esophagus where it belongs.
07:20
Now, let's move down
a little bit further
and talk about the larynx.
07:24
Here we have a nice sagittal view
that zoomed in a little bit here.
07:29
So we could see just a little bit
of the base of the tongue here.
07:33
So this is the most posterior
inferior portion of the tongue.
07:38
We also see a unique bone in
the neck called the hyoid bone.
07:44
And we see that flap of tissue
that helps move food
posterior into the esophagus,
therefore protecting our airway,
which was the epiglottis.
07:53
And from here, we're going
to start seeing the larynx.
07:58
A little bit further down, we have
a fold called the vestibular fold.
08:03
And just below that we have
something called the vocal fold.
08:07
As you might guess, by the name,
the vocal fold is actually
what's going to help create
vocalization or speech.
08:16
And then beyond the larynx,
we finally have the
lower respiratory tract
starting with the trachea.
08:23
And again, posterior to the trachea
is going to be the esophagus,
on its way down to the stomach.
08:32
Here we have a view from posterior,
where we've opened up the
larynx to look towards it.
08:38
So we could actually see
all of the epiglottis here
as this little flap that will
come down and protect the airway.
08:47
And as we go down a little bit,
we see both of these folds that
we called vestibular folds.
08:52
And we also call them
false vocal cords
because they look very
similar in location
at least to the vocal cords,
but they're not
producing any sound.
09:04
And it's actually just below these
that we have the true vocal cords
that are the ones that are going to
vibrate and produce sounds.
09:13
When we take a scope and
look down through the mouth
down towards the larynx,
this is the typical view
you're going to have.
09:23
And this is an
important view because
this is the view you would have if
you were trying to intubate someone
who wasn't able to
protect their airway
and needed some sort of
artificial help with breathing.
09:34
And this case, we see that
the vocal cords are abducted
or pulled away from midline.
09:42
Therefore they're open and
air can move in and out.
09:46
And from this view, you can
see that the false vocal cords
or the vestibular folds
are not only more superior,
but they're actually not
coming close to midline
as much as the true vocal cords.
10:01
You also see that unlike the false
vocal cords that are very pink,
the true vocal cords are
very bright gray or white.
10:11
So they have a lot of
different appearances
to distinguish them from
the false vocal cords,
which is useful when
you want to intubate.
10:18
Because when you intubate,
you want to get the cuff
that's going to expand
beyond the true vocal cords.
10:25
Because beyond that point,
as long as you have some
sort of way to deliver air,
nothing is going to obstruct
it from moving up and down.
10:34
And that's because at this point,
the true vocal cords
can become adducted
or come together and
close off the airway.
10:44
Beyond this point, we start
the lower respiratory tract
with the trachea and have a
clear path down into the lungs,
which we'll talk about
in the next section.