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