An Introduction to the Immune System

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our immune system functions to protect

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our bodies from harmful invaders but how

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exactly does it do what it does my name

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is leslie samuel and by the end of this

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video you're going to have a better

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understanding of how the immune system

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functions so let's do it

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[Music]

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[Applause]

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the immune system is a pretty complex

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system that includes a number of

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different cell types and organs the

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function is to basically block destroy

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or at least neutralize any harmful

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substances that can enter the body and

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when we look at the immune system we see

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that there are three lines of defense

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these are three different mechanisms

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that these foreign invaders need to

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overcome in order to get into our bodies

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to cause harm the first line of defense

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is the physical and chemical barriers

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then we have what's called the innate

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immune response which is non-specific

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and the adaptive immune response which

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is specific and more effective let's

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deal with the physical and chemical

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barriers first these are things like the

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skin that covers your body that's a

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physical barrier that pathogens have to

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find a way to cross in order to get into

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our bodies along with the skin we have

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sweat glands that secrete sweat and

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sebaceous glands that secrete an oily

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substance this helps to lower the ph on

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the surface of the skin making it more

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acidic as well as to wash away harmful

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stuff making it less likely that these

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foreign microbes will get into our

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bodies and have harmful effects then in

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our mouth we have saliva and saliva has

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different enzymes in it one of which is

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lysozyme now lysozyme is an enzyme that

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will actually break down the bacterial

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cell walls which is good because you're

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killing bacteria but let's say something

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makes it past your saliva and into your

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stomach well we have hydrochloric acid

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that's released in your stomach and that

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acidic environment makes it harder for

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those harmful microbes to even survive

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and then we have the mucous membranes

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these are mucus layers that line our

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digestive and respiratory tracts let's

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say you breathe in some kind of pathogen

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well a lot of those pathogens get

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trapped in the mucus and they don't get

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far enough inside to cause any issues we

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even have nasal hairs some of y'all got

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a little more than me

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but we have nasal hairs earwax and those

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will also trap pathogens again the goal

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here is to stop stuff from getting in

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that's our first line of defense the

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physical and chemical barriers we're

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trying to stop foreign invaders at the

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point of entry now obviously some stuff

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is gonna get past those barriers and we

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need to have some more protection on the

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inside so let's move on to the second

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line of defense and that is the innate

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immune response this is a non-specific

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response to those pathogens that manage

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to get past the first line of defense

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and it involves a variety of specialized

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cells and proteins they recognize and

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help to get rid of pathogens but in a

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more general way in this response we're

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dealing with phagocytes that will

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recognize foreign pathogens and they'll

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basically swallow them up using this

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process called phagocytosis

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first they bind the pathogen and then

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they wrap their cell membranes around

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the pathogen to take them in and once

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inside they will destroy the pathogens

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when those pathogens are destroyed

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they're basically broken up into small

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pieces and some of those pieces are then

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displayed on the surface of the

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phagocytes to be recognized by cytotoxic

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t cells which will do their job of

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destroying those phagocytes with the

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pathogen inside of them now we spoke

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about this a little bit in a previous

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video and we'll go into even more detail

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in a future video so make sure you're

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subscribed for when that comes out one

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more thing to mention about the

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non-specific innate immune response in

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addition to what we spoke about with the

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phagocytes and the t cells there are

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proteins that are part of what's called

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the complement system and no they don't

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go around like complementing bacteria

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and microbes and that kind of stuff but

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these proteins will get activated that

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was a dumb joke they'll get activated

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and when that happens they will recruit

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more white blood cells to the site of

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infection and trigger an inflammatory

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response which causes things like the

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redness and the swelling and the pain

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that's typical with inflammation really

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the goal here is to flood the area with

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more of the immune system components

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that's gonna help to fight off what

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could potentially be a pretty bad

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situation all right let's get to the

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specific adaptive immune response we're

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calling this specific because we're

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trying to eliminate specific pathogens

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that our bodies recognize because we

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were previously exposed to them it

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involves two types of white blood cells

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b lymphocytes and t lymphocytes aka b

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cells and t cells now we've spoken about

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these before and we'll get into a whole

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lot more detail in a later video but

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here's the short version of how this

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works b cells are part of our

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antibody-mediated immunity they

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recognize a specific antigen and then

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they bind to that antigen and digest

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that antigen and then they present

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fragments of that antigen on their

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surfaces to be recognized by helper t

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cells those helper t cells will then

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trigger those b cells to mature into

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antibody producing b cells aka plasma

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cells and now that we have more antibody

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producing cells the antibodies can do

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their part in helping to kill those

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pathogens this is called humeral

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immunity it's the specific part of our

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immune system that involves antibodies

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but there's also cell mediated immunity

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that involves the cytotoxic t cells aka

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killer t cells these are the ones that

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we spoke about earlier and they will

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recognize an antigen that's presented on

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the surface of a cell things like

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viruses and once they are recognized

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they will kill that virus infected whole

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cell so those are our three lines of

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defense the physical and chemical

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barriers the innate immune response and

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the adaptive immune response now i'm

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gonna go more in depth into the function

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of the t cells in the next video so if

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you want to know more about that make

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sure to check that video out i'll see

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you over there peace