An Introduction to the Immune System
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Transcripts
our immune system functions to protect
our bodies from harmful invaders but how
exactly does it do what it does my name
is leslie samuel and by the end of this
video you're going to have a better
understanding of how the immune system
functions so let's do it
[Music]
[Applause]
the immune system is a pretty complex
system that includes a number of
different cell types and organs the
function is to basically block destroy
or at least neutralize any harmful
substances that can enter the body and
when we look at the immune system we see
that there are three lines of defense
these are three different mechanisms
that these foreign invaders need to
overcome in order to get into our bodies
to cause harm the first line of defense
is the physical and chemical barriers
then we have what's called the innate
immune response which is non-specific
and the adaptive immune response which
is specific and more effective let's
deal with the physical and chemical
barriers first these are things like the
skin that covers your body that's a
physical barrier that pathogens have to
find a way to cross in order to get into
our bodies along with the skin we have
sweat glands that secrete sweat and
sebaceous glands that secrete an oily
substance this helps to lower the ph on
the surface of the skin making it more
acidic as well as to wash away harmful
stuff making it less likely that these
foreign microbes will get into our
bodies and have harmful effects then in
our mouth we have saliva and saliva has
different enzymes in it one of which is
lysozyme now lysozyme is an enzyme that
will actually break down the bacterial
cell walls which is good because you're
killing bacteria but let's say something
makes it past your saliva and into your
stomach well we have hydrochloric acid
that's released in your stomach and that
acidic environment makes it harder for
those harmful microbes to even survive
and then we have the mucous membranes
these are mucus layers that line our
digestive and respiratory tracts let's
say you breathe in some kind of pathogen
well a lot of those pathogens get
trapped in the mucus and they don't get
far enough inside to cause any issues we
even have nasal hairs some of y'all got
a little more than me
but we have nasal hairs earwax and those
will also trap pathogens again the goal
here is to stop stuff from getting in
that's our first line of defense the
physical and chemical barriers we're
trying to stop foreign invaders at the
point of entry now obviously some stuff
is gonna get past those barriers and we
need to have some more protection on the
inside so let's move on to the second
line of defense and that is the innate
immune response this is a non-specific
response to those pathogens that manage
to get past the first line of defense
and it involves a variety of specialized
cells and proteins they recognize and
help to get rid of pathogens but in a
more general way in this response we're
dealing with phagocytes that will
recognize foreign pathogens and they'll
basically swallow them up using this
process called phagocytosis
first they bind the pathogen and then
they wrap their cell membranes around
the pathogen to take them in and once
inside they will destroy the pathogens
when those pathogens are destroyed
they're basically broken up into small
pieces and some of those pieces are then
displayed on the surface of the
phagocytes to be recognized by cytotoxic
t cells which will do their job of
destroying those phagocytes with the
pathogen inside of them now we spoke
about this a little bit in a previous
video and we'll go into even more detail
in a future video so make sure you're
subscribed for when that comes out one
more thing to mention about the
non-specific innate immune response in
addition to what we spoke about with the
phagocytes and the t cells there are
proteins that are part of what's called
the complement system and no they don't
go around like complementing bacteria
and microbes and that kind of stuff but
these proteins will get activated that
was a dumb joke they'll get activated
and when that happens they will recruit
more white blood cells to the site of
infection and trigger an inflammatory
response which causes things like the
redness and the swelling and the pain
that's typical with inflammation really
the goal here is to flood the area with
more of the immune system components
that's gonna help to fight off what
could potentially be a pretty bad
situation all right let's get to the
specific adaptive immune response we're
calling this specific because we're
trying to eliminate specific pathogens
that our bodies recognize because we
were previously exposed to them it
involves two types of white blood cells
b lymphocytes and t lymphocytes aka b
cells and t cells now we've spoken about
these before and we'll get into a whole
lot more detail in a later video but
here's the short version of how this
works b cells are part of our
antibody-mediated immunity they
recognize a specific antigen and then
they bind to that antigen and digest
that antigen and then they present
fragments of that antigen on their
surfaces to be recognized by helper t
cells those helper t cells will then
trigger those b cells to mature into
antibody producing b cells aka plasma
cells and now that we have more antibody
producing cells the antibodies can do
their part in helping to kill those
pathogens this is called humeral
immunity it's the specific part of our
immune system that involves antibodies
but there's also cell mediated immunity
that involves the cytotoxic t cells aka
killer t cells these are the ones that
we spoke about earlier and they will
recognize an antigen that's presented on
the surface of a cell things like
viruses and once they are recognized
they will kill that virus infected whole
cell so those are our three lines of
defense the physical and chemical
barriers the innate immune response and
the adaptive immune response now i'm
gonna go more in depth into the function
of the t cells in the next video so if
you want to know more about that make
sure to check that video out i'll see
you over there peace
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