Changes in the Alveoli – Exudative Phase (Nursing)

00:01 This should look familiar to you.

00:02 But let's do a quick review because there's some additional key structures. I want to point out.

00:07 So I know that this is repetition and that's in there intentionally.

00:12 Remember you're studying with me as we go, so I can minimize the time you have to study outside of the video series.

00:19 Okay, so start the top tray set around.

00:23 That's the alveolar wall, one cell thick has two types of cells in the wall.

00:29 Type l, those are the ones that do the CO2O2 exchange.

00:33 Type ll, those are the short and squatty ones that squirt out surfactant.

00:38 Good deal.

00:39 Now inside the alveolus you see the other cell that's involved in ARDS, Macrophage.

00:45 Remember these are the cells if you have a direct injury to the lung, they're going to squirt out those cytokines.

00:52 Now keep moving down.

00:54 Now you see the capillary that is just snug around the single alveoli.

00:59 You know in real life there are multiple alveoli all squished together, but we extracted just one to show you so we could really break down and focus on the parts of it.

01:10 So you see the capillary, right? It's also a one cell thick membrane so that O2 and CO2 can exchange easily over that.

01:18 But two things I want to point out.

01:20 You've got an epithelial basement membrane and an endothelial basement membrane.

01:25 See their job is to kind of keep things all in the right place.

01:30 But look at that little space in between the alveolus and the capillary.

01:34 What's it called? Interstitial space.

01:40 Yeah, so when your patient has pulmonary edema, you got a lot of extra water in there.

01:45 It makes it really hard for them to breathe.

01:50 Can you see why? Well, if you feel that interstitial space with water and fluids and all this stuff in there.

01:59 You can't have the gas exchange between these two very good friends, the alveoli and the capillaries.

02:06 Okay, but let's look at that basement membrane.

02:08 Remember it's a thin extracellular matrix, right? Cool word.

02:13 Just means it kind of helps keep things where it's supposed to be.

02:17 Now, this gets damaged.

02:19 We got a havoc, okay? If the basement membrane is not intact, we're going to have some real problems in the oxygen exchange.

02:27 So I want to look at the changes in the exudative phase.

02:30 Let's take a look at what happens.

02:32 I forgot to point out here want you to take a look at, what are those little fellers in the bloodstream? Those are what we call PMN's - Polymorphonuclear White Blood Cells.

02:45 Cool, you got it.

02:46 Now if we filled in all the blood cells, you know, what other ones would be there.

02:49 There's five types of white cells.

02:52 You've got red cells, you've got platelets, but we're keeping it straight forward and clean.

02:56 I want it simple.

02:58 So your brain can focus on the key players.

03:01 But you know in real life, what would be flowing through that capillaries are all of the blood cells.

03:07 Okay.

03:07 So there's a healthy alveolus.

03:09 I wanted you to compare it too.

03:11 Yes, here's what goes on and something that is experienced ARDS.

03:16 I mean, how did we end up here? Well, look at the difference.

03:21 Now, you've got type l on both sides.

03:24 We've got type ll on both sides.

03:26 We've got a macrophage right in the middle to remind you there on both sides but, look at the difference, see that term alveolar flooding.

03:35 Whoa.

03:36 That is full of a lot of fluid.

03:39 There's no way this is going to be able to function as effectively as the healthy alveoli on the left.

03:46 Look at the difference in the interstitial space, and the healthy one is tight and even.

03:53 In the one that's in trouble.

03:54 It's starting to get bigger.

03:57 Look at that endothelial basement membrane on the left.

04:01 It's intact on the right.

04:02 We've got problems.

04:06 What is that PMN doing? What is that? Little guy is not supposed to be migrating, that's what they call it.

04:13 So this responder is migrating up through into the alveoli.

04:19 He does not belong there.

04:22 So let's walk through what happened? What is the process that we end up going from a healthy alveolus to this problematic, not efficient alveoli? So ready.

04:35 Let me walk you through step-by-step how we end up in this mess we call ARDS.

04:41 Now after the cytokines arrived, remember if it's a direct lung injury.

04:46 Who squirts out the cytokines? Right, the macrophages released the cytokine.

04:52 If it's an indirect lung injury, how do they arrive? Right, the cytokines arrived in the bloodstream.

05:00 So we're all on the same page.

05:01 The cytokines are here, right? That's what we're talking about.

05:04 Now, I want you to put your finger on the endothelial cells.

05:09 Where are those? So put your finger on the drawing on the endothelial cells.

05:14 So when these cytokines arrived, these cells are going to secrete some additional inflammatory molecules.

05:22 Now what these molecules do is they cause circulating immune cells like the neutrophils, to stick to the endothelial cells.

05:33 Got it.

05:34 Cytokines are there.

05:35 The endothelial cells from here in real close contact with the alveoli also got things in your bloodstream.

05:42 So what happens is those endothelial cells, it's their job.

05:46 They're doing the right thing.

05:48 They start secreting these other inflammatory molecules that cause the circulating immune cells to stick to them.

05:54 So see the neutrophils.

05:56 Those are some of the circulating immune cells that will stick to that endothelial membrane.

06:03 Now when the neutrophil stick to the altered endothelium, they can start to begin to migrate through that damaged capillary wall and into the alveoli.

06:13 That's how the PMN's get from the bloodstream into the alveoli.

06:19 Remember cytokines arrived, the endothelial cells start excreting the sticky substance.

06:24 So circulating immune cells stick to them.

06:27 It's damaging the walls when that wall is damaged.

06:31 Now this endothelium has been altered and now those cells can migrate through the damaged capillary wall and into the alveoli.