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- [Instructor] With all
those pathogens out,

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we have to figure out how
our body defends itself.

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One of the biggest defenses
is our lymphatic system.

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One of the main functions of lymphatic

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is the maintenance of blood volume

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in the cardiovascular system.

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And you're saying "Well, hold on,

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"how does that have anything
to do with defense?"

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Your white blood cells
are in the blood volume.

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That's part of your defense system.

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The lymphatic system can transport fats,

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fat-soluble materials, helps
with moving particles around

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through the blood is not as
easy to move around with.

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Filter out, or get rid
of the foreign particles,

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whether that's gonna be
pathogens that are living,

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pathogens that are
non-living, simply particles

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of cells that have broken down.

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Here's a snapshot of
your lymphatic system.

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The heart has the thymus gland on it.

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Thymus is gonna help out with immunity.

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Your throat, you have your tonsils.

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There's a ring of tonsils
all around your throat,

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which helps to try and deter any pathogens

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from coming in through either
your mouth or your nose.

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Your spleen, most of
your spleen will pull out

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dead blood cells or damaged blood cells.

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But it also helps through
moving micro organisms.

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Then we have our lymph nodes.

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Every kind of green dot
you see in the body there,

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each one of those green
dots is a lymph node.

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And there's even more than that.

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lymph nodes are meant to clean
out the lymph or the fluid.

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This way they can filter out any

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bacteria, particles,
pathogens, you name it.

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It goes into the lymph node

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and then if it's foreign,

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good chance it's not
coming back out again.

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Maybe when you've really been sick,

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you've noticed your
lymph nodes are swollen.

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Lymph nodes are around your neck,

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and if you're really sick your underarm.

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So there's a bunch of
lymph nodes all around.

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Then we have the vessels.

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The lymphatic capillaries,
right next to blood vessels.

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Let's start with how

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the first line of defense
of your body works.

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The skin, it really is
your first line of defense.

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It's a pretty good deterrent,

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things really can't get
through it very easily.

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We also have tears and saliva.

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They contain things called lysosomes.

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Then lysosomes contain enzymes,

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specifically antibacterial enzymes.

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So any bacteria that ends up going

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into your tears or your saliva,

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good chance is those bacteria

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are going to have a real problem,

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some will get through,

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but quite a bit will be killed off.

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Ear wax, might think of it
as more of an annoyance,

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But the ear wax, because of it's nature,

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actually entraps microorganisms

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not allowing them to proceed,

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not allowing them to live.

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Mucus...

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you're going to have mucus

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throughout your entire
oral cavity, nasal cavity,

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all down through your digestive
track and respiratory.

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Mucus is meant to trap microorganisms,

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but it is also meant to trap

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any particles that are entering the body.

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It is a way to try to
prevent foreign objects

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from getting into the system.

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Your stomach, you wouldn't
necessarily think of that

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as the first line of defense,

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but really the inside of your stomach

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is getting things directly
from outside environment.

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When you're eating,

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you're swallowing that outside component

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right down into your stomach.

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So, it is very acidic,
pH of two a lot of times.

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And that pH of two can inhibit

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quite a few different microorganisms.

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The vagina, obviously female specific,

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but were talking it's a little bit acidic.

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Now, this acidity helps to inhibit

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certain microorganisms from
forming and developing.

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Vomiting, urination, defecation.

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These are all ways of removing
objects from the body.

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They could be removing normal waste,

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defecation, urination.

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It could be a way of getting out

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any foreign particles, any bacteria.

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A lot of times vomiting,

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or more too frequent
defecations with looser stool,

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is trying to remove
microorganisms from the system.

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Your body is trying to flush out.

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Get rid of things.

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But, yet for all these defenses
you have resident bacteria,

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bacteria that live in and on your systems.

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Your skin is covered with
bacteria that should be there.

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Your intestines, specifically
the large intestines,

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have tons of bacteria that
are supposed to be in there.

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And these bacteria that are living there,

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a lot of times they can out compete

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any pathogens just entering.

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Not allowing those pathogens
to get a chance to even grow,

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because there is way too much competition.

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So with all this first line defenses,

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we do have some more secondary, third,

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and kind of beyond.

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If we look at our non-specific defenses.

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Phagocytic cells

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Now, phagocytic cells are
cells that are going to engulf,

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a lot of times they'll say
they'll eat other cells.

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They'll eat foreign particles.

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The idea is these cells are going

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to destroy what they
come into contact with,

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if they don't recognize it.

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So Neutrophils, Eosiniphils are two types

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of white blood cells.

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Macrophages, well they're
made from a white blood cell.

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All three of those cells
are meant to destroy.

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So this is how it works,

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in Phagocytosis, the phagocytes will

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basic capture a bacterium.

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That kind of pinkish pill
shaped thing is a bacterium.

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Then it is going to actually

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move the cell membranes around it.

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as the cell membrane are moved around,

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it'll completely surround and engulf.

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That bacteria that has now been engulfed

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will be inside a special vesicle.

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This way it keeps it isolated.

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It keeps it away from
the rest of the cell.

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While inside that vesicle,

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there will be these lysosomes

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that will then fuse releasing
their digestive enzymes.

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Those enzymes will break down bacteria,

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eventually releasing the waste.

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All the broken down particles

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that were a bacteria at one point,

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are now just individual building blocks.

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They're harmless.

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So, the cell will release those particles

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back into your system for
removal from the body.

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So, it really looks like the
cell is eating a bacteria,

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digesting it, and then releasing it.

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How about inflammation.

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Now these phagocytic cells
are going to go out and eat.

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Inflammation, cannot really do anything.

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It is just a swelling of an area.

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When something gets swollen,

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a lot of times it is also red.

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It might be a little bit warm.

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It might be painful to the touch.

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It depends on what the injury was

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and how severe it was.

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But, inflammation can occur
on various different levels.

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Could be a cut, could be a bruise,

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could be an impact, could be whatever.

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Any damaged tissues
can cause inflammation.

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Now, all this is meant
to help protect the area.

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The redness, the warmth,
the swelling, the pain,

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it's all a protective measure.

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So, here's how the
inflammation response works.

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First off, you have a site of injury.

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From a simple splinter, to a paper cut,

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to a knife laceration, to whatever.

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Something injured the tissue.

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The damaged cells release histamine.

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Now you might have heard of histamines

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as in you take anti-histamines.

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Yeah, you might take
anti-histamines for allergies.

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Well the reason you take anti-histamines

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are to try and stop this
process from occurring.

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When you have an allergic reaction,

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you have your allergies,
watery eyes, runny nose.

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That's your body's way of responding

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to an increase in a certain histamine.

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Well if you have a site of injury,

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you also produce histamine,

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which causes swelling in that area.

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It caused the blood vessels
to dilate or open up.

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By causing the blood vessels to dilate,

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it makes them larger.

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It makes them leaky.

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Things just leak out of them.

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As things are leaking out,

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you get this complement
protein that's leaking out.

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It's meant to identify

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and destroy the bacteria.

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So, complement proteins are meant

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to find bacteria and destroy them.

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Or, if nothing else,

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at least mark them for destruction.

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As the blood vessel opens up even more,

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it has even more leaks.

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Then the phagocytic cells will come out.

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Those phagocytic cells will
look for the complement protein.

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Wherever the complement protein is,

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they will attract

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and destroy wherever it's bound to.

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So, while the inflammation
might sound like it's backwards.

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Sudden injury, you got
cut, you want more blood?

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well this is why I want more blood.

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It is bringing particles in

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to fight off potential infections.

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It is bringing particles
in to stop the bleeding.