Chronic bronchitis pathophysiology | Respiratory system diseases | NCLEX-RN | Khan Academy

Voiceover: Before we get to exactly how

chronic bronchitis happens,

I just wanted to review a quick

rule of thumb about the body.

So this is any opening,

the body has to the outside.

Let's label this as the outside.

And anytime you have an opening

and irritants get into
the body, it could be,

by irritants I mean anything
that doesn't belong there

that inflames a tissue.

A common first defense
of the body is to call on

the glands which are embedded in tissue.

To secrete either liquid
or mucous into the space.

And the goal is to have
this fluid, this mucous

mixed with the irritants and eventually

flush them out or bring them out.

I'm sure you can think of examples

of what I'm talking about,

like tears.

If things get in your eye,

it makes your eyes tear, right?

So this is a mechanical thing

the tears actually flush out
the irritant in your eye.

And we have snot.

I'm sorry this is kind of gross,

but if things get in your nose

and it's not suppose to be there,

the snot has to bring it out.

And the third thing
which has to do with what

we're going to talk about today

is of course phlegm.

So when things get into
your throat or your lungs,

the walls of the lungs secrete the mucous

which forms a phlegm.

Now the system in the lungs also

triggers a cough reflex,

which so the walls here

if you can me drawing in red here.

The walls here are lined
with smooth muscle,

and when the area is being irritated,

the smooth muscle spasm

and that's how we get the cough reflex

to bring the phlegm out.

Now keep in mind, I
said this is the body's

first line of defense.

So these are good things to have,

you want the body to do this.

So chronic bronchitis is basically

too much of a good thing.

So we have over production of mucous,

such that the body cannot clear it

too much of a good thing,

that's when we have chronic bronchitis.

And of course itis just
means it's being irritated,

and bronch refers to the lungs.

So chronic inflammation and
irritation of the lungs.

Alrighty, let's draw some airway.

So we have our trachea,

the big stem bronchus branch
off into their branches.

Here you go, just keep going.

There are 20 or 30 branches to this,

you get the idea,

they keep getting smaller and smaller.

It's how our lungs expand.

And as you know oxygen goes into our lungs

and carbon dioxide from the body gets out.

So you have irritants in there

flooding what is usually a clear path,

then the lungs are not going to like that.

One of the most common chronic irritants

that we have in our lungs

is of course cigarette smoking.

So, here we go, we're going
to light this cigarette.

And where you see a smoke
rising from the cigarette

is actually billions and
billions of particles

that can enter and lodge into our lungs.

As a response the glands
in the side of the walls,

they start secreting the mucous.

Remember it's part of our normal response

to irritation.

But of course chronics,

we're talking about years
and years of constant.

Everyday it's like this.

Now eventually, what's
suppose to be a clear pathway

becomes convoluted with the mucous.

It's like, if you're drinking
through a straw from a cup,

instead of having a clear straw,

you're sucking on a milkshake.

So this milkshake is thick
and it's clogging the straw.

So you'll have to suck harder

and work harder to get through.

Likewise, with the mucous,

sometimes there's so much build up

that it can clog off one
little branch of the lungs.

So no more gas exchange
can take place here

and depending on the
severity of the disease

you can have different areas of the lungs

being out of commission
because of the mucous.

Now of course we always
talk about smoking,

but there are other things

that can lead to chronic bronchitis.

One important thing is pollution.

Again pollutants are also billions

of particles in the air all the time.

In some countries that's
especially a big problem

and chronic bronchitis
is very common there.

Or we can have coal dust,

for people who work in coal mines,

or people who work with asbestos.

Shipyard workers.

The common theme here is

it happens when we can inhale irritant

and it happens everyday.

Now if I just smoke for a few days

and I have a lot of mucous,

that doesn't qualify me for
having chronic bronchitis.

The pathophysiology here talks about

the overgrowth of the glands.

So we actually look for tissue change.

Now in a patient, to
diagnose chronic bronchitis

is usually a clinical diagnosis,

which means there are no test,

it's just from the story.

But we know from examining lungs of people

who have passed away,

the tissue change actually happens.

So I just blew up one
branch of the airway here.

We'll call this the lumen.

The lumen just means
the inside of the tube.

So the lumen is here,

where the air is getting through.

So the black space on both sides

are the walls of the bronchi.

So basically if we take a
cross section of our airway,

in the middle here is the lumen.

And right now I'm going to talk about

the wall space of the bronchi.

Okay so we have some smooth muscle

around the walls.

Again this spasm in this

is what gives us the cough reflex.

And right near the
surface close to the lumen

we have these layers of glands.

They're responsible for
the mucous production

we've been talking about.

As you can see they are
right under the surface.

The job is to secrete
things into the lumen.

Okay just for completeness

let me draw some irritants in the lumen.

Okay.

So that's what a normal
wall usually looks like.

There is a way for us
to put a number on this.

And we only do this,

we've only seen this in
people who have passed away

and their lungs get caught up in the lab,

and we can look under the microscope

to see the Reid index.

Which is a way to calculate
the ratio of the glands,

the thickness of the
glands to the whole wall.

Now normal Reid index is less than 40%.

So we can see the thickness here

versus the thickness of this whole wall.

It should be less than 40% in you or me.

And of course in the middle here

there are other things like cartilage

or connective tissue.

We're just going to
fill it in a little bit.

Now what happens in chronic bronchitis is,

the actual thickness of
the gland layer grows.

So the glands start proliferating,

because we need so much mucous

that the original number is not enough,

so the body is recruited
to make more glands

and they extend towards the smooth muscle.

So in chronic bronchitis,

the Reid index is usually over 50%.

So definitely more than
half of the thickness

of the whole wall is made of glands.

Now remember we cannot
do this in living people

because we have to cut away their lungs.

So just a way for us to put
a number on this disease,

but usually the patients are diagnosed

and treated according to their symptoms.

And the symptoms all come
from this tissue change

and the over production of mucous.