Hi, welcome to our video series on life threatening lung conditions.
In this one we're gonna talk about the role of surface tension and surfactant.
This is one of my favorites.
So let's talk about surface tension, because surface tension increases the risk of the alveoli to collapse
and I'm gonna help you understand why,
because liquids have a tendency to shrink into the minimum surface area possible.
Take a look at that alveoli.
There should be some old friends there that you recognize from the rest of our video series.
You've got the wall, its one cell thick.
You've got the type 1, the long and elegant; and the type 2, short and squatty.
So you've got the two types of cells in the wall,
but we've got something else that I wanna bring to your attention,
because that's actually lined with water.
Now, thinking about surface tension, it always wants to shrink into its minimum surface area possible.
Now, what surfactant does is it decreases the surface tension in the lungs
and because it decreases the surface tension in the alveoli, in the lungs,
it decreases the work of breathing because it minimizes collapse and edema.
A lot of words. Let's see what that means.
Well, if I want to be able to take a full breath,
I need most of these 600 million alveoli I have in my lungs, to be able to be open, right,
I need them to be available to receive air.
I need them to be able to touch the capillaries so that they can exchange CO2 and oxygen,
that's what surfactant does for me,
so I need it to minimize the risk of too many of these guys collapsing.
I also don't want it to be edematous.
If my alveoli is full of extra fluid, I can't get that very good exchange of oxygen or carbon dioxide.
So, what plays a big role in that?
Surfactant, we're gonna be saying that a whole lot as we go through this part of it.
Now, do you remember where surfactant comes from?
Right, those Type II great alveolar cells, right?
Remember, they're granular, they're roughly cuboidal and they cover about 5% of the alveolar surface.
Now, these are the little fellers that secrete pulmonary surfactant.
Think back, what type of cells are in the wall? Type I and Type II.
Type I cells are responsible for the gas exchange, Type II are the ones that makes surfactant.
So take a look at our picture.
You notice we've added some things at the alveoli to the inside linings
since the last time we showed you this in our video series.
So you've got the wall that you recognize, look at that line of blue all around the inside, that's the water.
But, if you look really close, there's some little yellow circles with tails on them that represents the surfactant.
Remember that helps me minimize the risk of collapse,
keeps that structural integrity, it's really, really important to healthy breathing.
Well, here's something I would be uber impressed if you knew.
How long does surfactant last and then what happens to it?
Yeah, I didn't expect that you would know that, so let me tell you
because this is how nerdy I can get.
The half-life of surfactant is 5-10 hours once it's secreted.
Who secretes it? Right, Type II cells, they make up about 5% of the wall.
You'll hear me keep repeating these facts for you, so we're studying together as you go
because I want you to be successful and I know what I can do to help you get there.
So up to 90% of the surfactant is DPPC, no, I am not going to spell that all out, it doesn't matter.
It's not worth your brain cells, right?
I don't want to tie up your real state with being able to spell out what DPPC stands for,
but about 90% of it is recycled. Hey, pretty cool, right?
Look at your alveoli can do, they're very green,
so they recycle about 90% of it from the alveolar space back into the Type II cells.
So half-life, 5-10 hours and up to 90% of it gets recycled back into the Type II cells.
So what happens to the other 10%?
There you go, remember, our friends, the alveolar macrophages?
Well, they take up the other 10% and they do what they do, they swallow it up and they digest it,
because remember the macrophages are phagocytic cells,
they swallow things and they're part of your immune system.