It's frequently thought of as a bad thing, and that we need to do everything we can in order to get rid of it.

But inflammation is actually about healing.

And so when inflammation is working properly, this is a good thing and it's absolutely necessary.

Because without this incredible process, we would not survive.

Now, it is true that there are situations where inflammation can become chronic with specific inflammatory conditions and certain lifestyle choices.

But today, let's first talk about how inflammation is supposed to work by discussing some of the amazing signals that your body utilizes when it's injured or under attack.

And how these signals change your blood vessels, change your white blood cells, and promote this incredible natural healing process that we call inflammation.

It's going to be an inflammatory one.

So let's do this.

Inflammation Now, all of us have experienced inflammation in some form.

Maybe it was from an injury like an ankle sprain, a splinter in your finger, or some sort of pathogen like bacteria that's trying to invade you.

But regardless of the cause, there are some common signs of inflammation which include redness, swelling, heat, pain, and sometimes loss of function.

Like with an ankle sprain, you've likely experienced all of those signs, including the temporary loss of function with that joint.

Or maybe you've had a pathogen infect your tonsils, and they got red, hot, swollen, and painful.

And what we're going to find is that all of these signs of inflammation have a purpose.

Or in other words, can be explained by the steps of inflammation that we're going to cover now.

So let's use this picture to help us with this.

So, as you can see, we have a tiny little blood vessel here called a capillary.

And inside the capillary, you have this cell representing a white blood cell called a neutrophil, which is doing this really cool roly-poly process that we'll get into during the next step, and we'll find that it's not really called the roly-poly process.

But outside the capillary, we have some tissue cells that I've taken the liberty of drawing in myself.

And as you can see, they are sad and injured.

Now, as I mentioned earlier, this all starts with some sort of tissue and cellular injury.

And this injury could come from trauma, where connective tissues and cells are damaged and torn apart, or from a pathogen like bacteria that could release harmful toxins.

And we are representing these scenarios here with this star-looking inflammatory explosion.

But this injured tissue will release multiple substances.

And we have some of those substances labeled here as these blue cytokines.

And these cytokines will initiate the inflammatory response by signaling to nearby troops as well as distant troops that it's time to go to war.

And these troops are your white blood cells.

The first white blood cell that gets called into action is a tissue macrophage, which I've drawn here as this large blob cell with a purple nucleus that actually kind of looks like a mouth, but that kind of works because this cell is going to engulf things.

Don't judge me.

I'm not an artist.

But this response to these damaged cells occurs within minutes because a tissue macrophage is a local macrophage that resides in the actual tissue in this area.

And this is really cool because essentially, you can think of it as your body stationing troops, these tissue macrophages, in the tissues throughout the body, just in case something like this happens, so that you can have an immediate response, again, within minutes.

And these tissue macrophages participate in a process called phagocytosis, which translates to cellular eating.

They can engulf dead tissue, cellular particles, as well as pathogens such as bacteria.

And this step takes place during about the first hour of inflammation.

Now, this first step with these tissue macrophages is very important and even life-saving.

But the number of these tissue macrophages is not very high.

And so there isn't enough of these troops, especially in more moderate to severe injuries and infections.

But luckily, those chemicals or those cytokines that were released at the start of inflammation also signal to more distant troops for additional backup.

And after about the first hour of inflammation, large number of neutrophils, another type of phagocytic white blood cell, will start to infiltrate the inflamed area from the blood.

This infiltration was caused by those inflammatory cytokines.

And for you physiology nerds out there, maybe you've heard of some of these cytokines like tumor necrosis factor and interleukin-1.

But these names are not necessary to have an understanding of this process.

But these cytokines and other biochemical products produced by the inflamed tissues initiate some really cool processes that allow for this infiltration of the neutrophils to occur.

First, as I've already hinted to, the cytokines attract the neutrophils to this actual site of injury.

Kind of like putting up the bat signal or radioing for backup.

And using these chemicals to attract the white blood cells to this site of injury is referred to as chemotaxis.

Second, these cytokines also cause increased expression of adhesion molecules on the surface of the endothelial cells that are near the site of inflammation.

Now, endothelial cells are just the cells that line the capillary.

But if you look at this picture, we can see that these adhesion molecules on the endothelial cells, one of which is called selectin, and the selectin will interact with the integrin molecules on the surface of the neutrophil.

And this essentially will cause the neutrophil to get stuck or adhere to the capillary wall so that it doesn't get pushed past the site of inflammation with the blood flow.

What is also happening at the same time is that the cytokines and other inflammatory signaling molecules cause the capillary to vasodilate, which is to increase the diameter.

And this brings more blood and therefore more neutrophils to the site, as well as causes the intracellular attachments between the endothelial cells of the capillary to loosen, creating larger gaps between the cells.

And this increases the permeability of the capillary, which will cause more fluid to leak out of the capillary and into the site of inflammation.

But it also allows our roly-poly process to occur where this neutrophil army can kind of army crawl across the capillary wall and then squeeze through the cracks between the endothelial cells.

And now, poof!

These neutrophils are now at the damaged tissue site where they can help those tissue macrophages defend and clean up the area through phagocytosis.

Now again, it isn't technically called the roly-poly process.

And the names are, again, not really as important as the concepts.

But for those of you that love names, when the neutrophil adheres to the endothelial cells, this is called marginination because it attaches to the margin of the capillary.

And when the neutrophil squeezes through the cracks between the endothelial cells, it's called diapoditisis.

Dia means through.

Poditisis refers to leaping or jumping.

It's more like squeezing than jumping.

But we don't need to get lost in all that.

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And now, let's get back to inflammation.

Now, let's have a little bit of a checkpoint here.

One, if you had to pinpoint one of the most important take-home messages about inflammation, it is this process that we just saw.

Getting these white blood cells to this site of injury or infection so that they can clean house and initiate the healing process.

And we are also starting to see why we experience some of the symptoms of inflammation such as red, warm, and swollen.

Remember, I said that the capillaries vasodilate and the spaces or the cracks between those endothelial cells get wider.

And this led to not only the neutrophils getting out of the bloodstream to the site of injury or infection, but also allowed for fluid, some of the plasma from the blood, to leak out of the capillary and into those tissues.

And this is what accounts for the swelling and the increased warmth and redness.

The swelling can also lead to some pain and discomfort as the tissues and nerve endings start to get compressed and stimulated.

There's also an interesting distinction between inflammation caused by trauma or injury versus inflammation caused by some sort of pathogen such as bacteria or viruses.

With both scenarios, you get the process that we've described so far.

But with an injury, say like an ankle sprain, you also add some additional damage.

And what I mean by that is with something like an ankle sprain, you're literally tearing through tissues such as ligaments.

And the severity of this tearing can obviously vary based on the severity of the sprain.

But you will also potentially tear through capillaries that supply that tissue where whole blood literally spills out of those torn capillaries.

And this will typically contribute to even more swelling as well as the addition of bruising because now you have red blood cells and other components of the blood spilling out of the torn capillaries that don't typically spill out of the intact vasodilated capillaries that you would see with, say, something just caused by a pathogen or I should say inflammation just caused by a pathogen.

And obviously, tearing through soft tissues with injuries is also going to come with some additional pain.

But again, in either scenario, bringing the white blood cells to the site of injury or infection is one of the most important parts of this story.

So much so that we actually even have a second wave of white blood cell troops sent to the tissue.

Within a few days of inflammation starting, a white blood cell known as a monocyte will come from the blood and enter into the inflamed tissue.

Now, you might be thinking this monocyte is a completely new cell.

But you have met this cell before, but in a different form.

You see, a monocyte is kind of like your Bruce Banner to the Incredible Hulk because once the monocyte squeezes through the capillary and enters the inflamed tissue, it says to the inflamed area, you won't like me when I'm angry because I totally imitated that voice correctly.

And it starts to get bigger and bigger and angrier and angrier and it becomes a larger Incredible Hulk macrophage, smashing and engulfing every bacteria, virus, necrotic tissue, or other foreign particles in the tissue.

Yes, that was a little dramatic.

But the point is again, a monocyte is essentially a macrophage.

And this is how it was taught to me when I was a wee high school lad that a monocyte was kind of the Bruce Banner to the Incredible Hulk macrophage.

So hopefully that kind of helps you remember that.

But when we have this monocyte getting bigger and becoming a macrophage and entering this inflamed tissue, this is important because macrophages are more powerful phagocytes than neutrophils, often capable of phagocytizing as many as 100 bacteria.

Macrophages also are capable of engulfing dead particles, larger particles than neutrophils are, whereas neutrophils can only usually engulf or phagocytize about 20 bacteria before the neutrophil becomes inactivated and actually dies.

But macrophages, after digesting particles, can extrude or get rid of the residual products of digestion and often survive and function for many more months afterwards.

Macrophages also play an important role in initiating the development of antibodies.

However, that is a topic for a whole other video.

But neutrophils are still very important to this process because remember, step one to this whole process was those tissue or resident macrophages that were already stored in our tissues and this allowed for an immediate response.

But those tissue macrophages were only stored in a small amount.

So we called for backup in step two and that was those neutrophils.

And the reason this is so important is because our body has many more neutrophils circulating in the blood than we do monocytes.

And so this allowed for that first wave of backup, those neutrophils, to get to the inflamed tissue within about an hour to help hold down the fort, so to speak, until our red bone marrow could start making more monocytes.

And it takes a few days to build up a significant amount of monocytes.

So again, those neutrophils are significant in those early stages of inflammation.

And so now what?

We have these macrophages and neutrophils engulfing pathogens, dead cells, tissue particles, and debris.

What happens when this mess is cleaned up and everything's been engulfed?

How does inflammation resolve?

Well, this is where your lymphatic system plays an important role.

In your tissues, you have another type of capillary called a lymphatic capillary shown in green here.

And these lymphatic capillaries are important because they are even more permeable than the blood capillaries, which makes it easy for large stuffed macrophages to squeeze into.

And also very important, this greater permeability of the lymphatic capillary makes it even more capable of draining all of that excess fluid that contributed to the swelling.

And so this is when you start to notice the improvement in swelling.

And something else that is also very cool is that as the lymphatic system drains this area, if there were, say, some bacteria that ended up evading and didn't get engulfed by the macrophages or the neutrophils, once they get pulled into those lymphatic capillaries, these lymphatic capillaries merge into lymphatic vessels that flow into little swellings called lymph nodes.

And guess what's in there?

Even more white blood cells to do any extra killing or filtration that didn't get fully taken care of at the initial site of inflammation.

And we actually recently released a video on the lymphatic system that goes into even more detail that I'll link at the end of this video.

But one of the last things I want to mention here is that you have likely heard, at least in the case of inflammation due to an injury, that you can help speed up this process with things like rest, ice, compression, and elevation, often referred to as the Rice Protocol.

Now, icing immediately after an injury can be a little controversial.

Those that are against it will say, we don't want to vasoconstrict those capillaries with the ice because that could possibly blunt the early stages of inflammation of getting those white blood cells to the area.

And there may be some truth to that, but ice can help with pain a little bit.

However, you certainly do want to rest the affected area for a few days depending on the severity.

But what about compression and elevation?

Well, both of those can assist with the lymphatic drainage.

Your lymphatic system is a low-pressure system.