chapter 21 part 1 Dr. Parker

yeah for some reason when we start to talk about the immune system people immediately think oh my god this is hard and students for some reason every semester just absolutely hate the immune system and I think it's going to be the hardest thing in the world it is not a complicated system there's absolutely no Anatomy that we have to learn in the immune system there are no organs of the immune system the immune system is simply how a very small group of cells work throughout our body and they work together okay what's amazing about it is how a cell in my big toe can know what a cell in my shoulder is doing and they can they'll communicate with each other they build armies to protect you the job of the immune system is to fight off any incoming pathogen okay a pathogen is anything in your body there's not supposed to be there that can make you sick okay a pathogen can be a bacteria which is the most common pathogen but a pathogen can be a worm it can be a eukaryotic cell like a fungus those can all be pathogens so if any of those here in your body they're not supposed to be there your immune system mounts and attack all it takes is one of your immune system cells finding one microbe that's not supposed to be there and it immediately attacks what's one cell recognizes something that's not supposed to be there and attacks it it immediately starts secreting chemicals that go into your bloodstream and that tells every other cell in your immune system that something has been found and all the other cells start rushing to that area to help so which is exactly what we were going to do if we were going to fight somebody if there were 50 people that we're trying to fight me and I was by myself what is the first thing I'm going to do let's start yelling and calling for help right so when when your immune system sees a group of bacteria stop so severe they may start fighting the day immediately start calling for help and all the other cells rush to help them okay in order to get through the immune system we got to kind of go through a hierarchy you always start with the innate immune system and then the adaptive immune system anytime a microbe invades your body your innate immune system attacks it first if the innate immune system can't handle it that's when your adaptive immune system usually comes into play your innate immune system is something you are born with okay every baby is born on Earth has an innate immune system now your innate immune system can get stronger as you get older but the one thing your innate immune system does not do is it never learns okay so what does that mean how can I say learn your innate immune system could care less what it's trying to kill it doesn't recognize oh I've seen this before and it's an e.coli your innate immune system cells just say this is not supposed to be here I'm getting it out I don't care what it is okay the adaptive immune system that is what you develop as you age it has a memory component to it when you're born you have an adaptive immune system but it doesn't know what to do because it hasn't seen anything yet as you get older you are exposed to more and more types of microbes and those cells in your adaptive immune system will learn what those microbes look like and they can fight them faster if you come in contact with them again okay that's example I can give you before we get into the details how many of you have had chickenpox almost everybody in the room right can you get chickenpox again nope does that mean you'll never inhale the chickenpox virus again of course not your your kids make it to him Hawks one day right you'll inhale the virus again it's actually still in you but that's a whole other discussion so if you can still inhale it why can't you get it because your adaptive immune system knows what it looks like and if you inhaled a virus again your adaptive immune system cells immediately recognize and say nope I know this is bad and kill it before I can do anything to you okay why if you get the flu once in a year you don't get it again unless the flu mutates which again becomes another discussion but usually once you get something and you're getting sick from it the first time if you can get it again it's much less severe if you can't even get it again okay and while we're discussing that we're also going to talk about how vaccinations work because I don't think a lot of people really understand we just go and let them focus up in our arm and say thank you you kind of need to have an idea of what they're shooting in your arm or your kids arms okay so first we're going to go through innate immune system if there's two lines of defense the first line and the second line okay then we'll get to adaptive immune system with our first line of defense this is the easiest thing in the world to understand your first line of defense in your body is your skin and your mucous membranes they form a physical barrier that makes it almost impossible for microbes to get inside of your body your first line of defense is very hard to get past do you think that a pathogenic a microbe that can make me sick is going to touch my arm today yes very likely one's going to touch my arm but is it going to make me sick probably not because my skin is a solid layer of stratified squamous epithelium right remember epithelial cells are connected together they don't let self pass back and forth the ones on the outside are even dead and full of keratin right so there's no way it's getting in there the only way can get past my skin is if I cut my skin or inside aside that looks like a really fun pimple and I decide I have to start squeezing on it hey we're all Staphylococcus aureus is that a bad mean bacteria no it's not every one of you have it on you right now it's on your arm it's in your nose it's in your mouth it's in your intestines it's everywhere in your body but you don't all have a staph infection right because it's living where it's supposed to if it's on my skin right there it's not a staph infection you get a staph infection when the staff gets underneath your skin long just above your skin it doesn't do anything to you really easy way to get that infection is to pick it something you pick and pop a pimple and your hands are dirty or you push some staff from your skin into that hair follicle then you can get a staph infection the bacterial itself is not bad it's just it can hurt you if it gets under that skin okay go ahead the same reason people were once convinced that the earth is flat but I mean just don't know any better same reason people believe that if you eat sweet and while you're eating a cancer that's not true either that's just that you hear stuff on TV okay the same reason people think that regardless of which presidential candidate you want to vote for they're going to fix something neither one's going to fix anything right whatever they say in the news we believe it's just not true so since you guys are educated y'all are supposed to teach people better that's your job even though they'll argue with you because they didn't give you the entire virus and that's what we're going to talk about vaccinations a little bit it's a really giving you the true smallpox virus on your skin it would have spread they gave you a little piece of it just enough of it to activate your immune system but not make you sick and that's why and that's generally what we do was shot it's most vaccinations it's impossible to get sick from them there are a few that are live but there's very few that are okay right your skin is not the only portion of your body that is constantly in contact with the outside of the body with the world right what else is I don't have skin covering inside of my mouth inside of my nose what's covering that mucous membrane okay because nobody not quite as tough as your skin but there's something on them mucus is there how does the mucus help if I inhale bacteria what if my mucus do catches it the mucus catches it and it have a little cilia in my respiratory tract does cilia bring it back up I either swallow it and it goes away or I blow it out of my nose or it gets trapped in my nose hairs mixed with mucus and it becomes a a booger right so all that is below your first defense of your immune system works your first line in a sense I said that you invited be so disgusted like I couldn't believe I said booger you've all picked the booger trust me when you were - that was your favorite thing to do was pick a booger I promise okay so I put the focus on the defense it's easy right there's something physically they're keeping the microbes from getting in well what if they do get in do they get in often yeah they do but they still don't make us it even though they get in and that's because if they pass our first side of the fence our second line under the fence is ready to go your second line of defense is made up of cells that work together to fight the infection the two most common types of cells you have fighting infection for you are neutrophils macrophages where our neutrophils and macrophages found what's a neutrophil on a monocyte a white blood cell very good so they're normally in your blood okay well when something sometimes those monitors lights will migrate to different tissues come out of your blood well once they leave your blood decide hey this area right here under the skin looks good I'm gonna hang out here for the rest of my life that's when we call them a macrophage okay the neutrophils are in your blood floating around and when the macrophage finds something they'll call for help and the neutrophils can then come out of your blood okay so we're talking about things that are usually diffusely spread through your body but they can come where they need to come when we need them to fight something okay they both work by phagocytosis okay and what is phagocytosis once they eats another so let's make it look a little bit more scientific than one so eat another so okay so this big purple blob on the picture is supposed to be a phagocytic cell so that could be a neutrophil or a macrophage they work exactly the same way okay the first thing that has to happen do phagocytic cell is going to bind to the pathogen now in this picture this is the bacteria so this macrophage or neutrophil has found a bacteria that's not supposed to be in your body and they grab a hold of it it's way cooler than this little cheesy drawing looks okay the cells will extend long pieces of their membrane and their cytoplasm out grab a bacteria and then slowly pull it in to their body and I really do do this we have electron microscope images watching them do this it's like science fiction they reach out and grab the bacteria and start pulling it in and there'll be another set of arms coming out of this side of the cell grabbing another bacteria pulling it in okay once they caught it and pull it in now the bacteria is inside of the phagocytic cell inside of a little vesicle we call this the phagosome we can't do anything to the bacteria and a phagosome but do we have an organelle inside of every one of our uses in our body that has a little digestive enzymes in it yes what's it called lysosome so here's what they do they take the saga film fuse it with a lysosome so now we have a phago lysosome okay just cheesy naming but what's happening is what's really neat all these will digestive enzymes start breaking the bacteria down into little bitty pieces okay once we get the bacteria broken down into just pieces it can't hurt us those pieces are then spit out of the phagocytic cells they'll eventually travel through our lymph or our blood one or the other and eventually just excreted out of body because in these teeny tiny little pieces that can't do anything to us it's just a waste product okay it's pretty neat right that's not even all that it can do to give you a little preview of something we're gonna see when we get to the adaptive immune system these guys are actually going to help the t-cells and b-cells work your b-cells and we're going to find all this in detail later but just to how your notes will be complete okay your b-cells are going to respond to those little pieces that are spit out by the phagocytic cell okay so I'm really neat not only does the phagocytic cells stood out these little tiny waste pieces he'll take a few of them move them to the surface of his cell and stick them out on the end and hold it out there like a flag that's waving and then the t-cells will come and respond to it so your T cells and your b-cells can't do anything unless this phagocytic cell finds something breaks it down Foreman says here it is alright here's I'm on hold it this way 55 and I will put the little pieces out for the B cell so that they can both come do their job okay that makes sense you know micro class with me you've seen this picture before I see the many different regardless of which class you take the immune system is the immune system okay now phagocytic cells are not the only cells that are part of your second line of defense there are others the phagocytic cells are the ones we're going to talk most about but I want to give you an idea of what some of the others do there are Falls in your second line of hints called natural killer cells what do you think they do they kill they're the natural killers in your body they kill cells that belong to you why would I need a cell to kill myself because let's say one of myself did something wrong what if one of my cells as it was trying to divide didn't copy the DNA correctly that's now a cancer cell there's something wrong with myself the natural killer cells are pretty amazing they can recognize oh this is a Mandy Parker cell but it looks weird so I'm gonna go ahead and kill it if you think about it that's actually pretty amazing that it can recognize that and know when to kill it and when not to kill it all the other cells in your immune system if it's one of your cells they just ignore it because they're trained to not kill your body cells but the natural killer cells can cancer is not the only time that natural killer cells work just to give you an idea so you may not know but when a virus infects your body the virus physically goes inside of your cell replicates in your cell and then kill yourself urging thousands of viruses out okay we can't kill that virus but what we can do to slow it down is the natural killer cells can kill your cell while the virus is in it so that's their two main jobs if they find a cancer cell or they find a sale instead a virus in it they kill it they do it by something called apoptosis which is considered programmed cell death they don't just graduate cure it and the soul just burst and all the pieces are released that would be wasteful apoptosis is a programmed way to kill the cell so the cell will slowly start to break down the DNA then slowly break down the proteins the membrane will slowly degrade it does that so that we can use any pieces that we break down it's not just a rapid burst it does have some until I fancy er than what I'm explaining it but it has some self check mechanisms it can actually start killing the cell and if it realizes it's wrong it can stop and the cell may be able to repair so it's a it's a pretty complex mechanism so that's one other type okay now let me do I'll come back to that okay couple other things we have in our second line of defense we have something called interferon its term pair ons are not cells they're proteins but their job is to help get rid of virus infected cells in your body they are proteins made in your body to kill virus infected cells now the only reason I bother telling you what this is is because some of you have probably taken and interferon before and I think if you're going to take it you should know what it is have you ever heard of Tamiflu Yeah right you take that when you get the flu the flu is a virus you can take every antibiotic in the world and it's never going to kill the flu virus antibiotics only kill bacteria so when you get the flu there used to be nothing we can do about it except wait for it to go away okay but when we discovered that our body naturally makes these proteins called interferons that can stop a virus from replicating we purified those out of humans we kind of copied what they look like and now in a lab we make synthetic interferon so if you've ever taken a medicine for a virus you were taking an interferon and they were that something your body naturally makes we just took them out and made so that so we can really inject you with it okay a lot of your um if you've ever taken the Appeals for Coke cold sores those are interferon okay all right the other type of protein we have in our body that is a helper is called complement complement is real real complicated so we're not going to go in till into detail I can remember spending about six weeks talking about complement when I took immunology in college it were six weeks of my life so here's what I want you to know complement complements the activity of all the other parts of your immune system which is why it's named complement so if there's a neutrophil eating a bacteria this nice host be their complement will come over there and help say oh you're trying to eat this here and then they'll arrange and they'll poke a hole in the cell but the phagocytes trying to eat they help it if your t-cells trying to kill something the complement will go help if inflammation is occurring the complements kind of go help so I just want you to be familiar with the word and understand you know for your future class as you Teddy that's going to be something that's going to help everything else go on there are times when these cells organize together instead of just working by themselves okay the process with all these cells and proteins and your second line of defense working together it's called inflammation so if I just straight-up ask is inflammation bad or good what's answer I mean again most people are going to say it's bad right in my opinion is good some of you've had me for a teacher before and you know what it's good right if I cut myself is it very likely that I'm going to get bacteria in my body yes because even if I cut myself with a sterile knife there's bacteria on my skin so if I cut myself most likely that care is getting in there if I cut myself and it doesn't inflame it all that worries me information is the Sun that your body is working to fight whatever has gotten in there okay so I'm going to explain it in layman's terms and then I'll teach you what the real terminology for everything is okay so in our picture right here this genius has taken a nail and stabbed it through his skin okay I say he because a woman would never do this so see here I've been out there his skin do you see the top part of this is the epidermis it's through the epidermis down in the dermis so those little green bacteria they've made it past the first line of defense the very first thing that's going to happen now that those bacteria are down in the dermis the phagocytic cells that are in the dermis the resident macrophages are going to see it and say this isn't supposed to be here they're going to grab it and start eating it well they can't do it by themselves so also stockist entrails eat the first bacteria they start releasing chemicals calling for help help comes to the area from the blood vessel that's running through your dermis okay whenever the chemicals are received in the blood the blood vessel starts dilating what does that mean getting bigger in diameter when my brother gets bigger in diameter just more blood flow into the area or listless more blood starts flowing into the area right as more and more blood flows to this area where inflammation is occurring it's bringing more and more Souls with it so the area turns red because of more void flow the area gets hot because of more blood flow okay a lot of people would like to tell you oh I got inflammation there fever in it that means it's infected well yes and no that means it's infected but that means your immune system is fighting the infection so it's actually not a bad thing for there to be warmth in the area okay as all this extra blood starts coming to the area it brings neutrophils with it the neutrophils sense the chemicals that were released from that first phagocytic cell and they start scooting towards the edge of the blood vessel wall as they pushing it closer to the edges of where that's a wall they can squeeze out of the blood vessel go into the area and then they all start eating the bacteria that aren't supposed to be there okay as all of this stuff is leaving the blood and going into the area underneath the skin what's going to happen to this area when it fills up with all that extra stuff it's going to swell as it swells you get pain because you have stuff pushing on your pain receptors okay so a lot of you at some point probably memorize the four cardinal signs of inflammation I think you should be able to tell me why those four things are occurring it's red and it's hot because of all the extra blood flow it is swelling because stuff is actually leaving the blood and coming into the area to help mount an attack I always use the cheesy army terminology but the army is coming to the spot to help you fight all right the pain comes from the extended war vessels and all the stuff in the area pushing on all your pain receptors okay so if I cut if I had done this to myself I had stuck myself with a nail and I'm started seeing pulse in there is that as guess what passes pulse is cell debris and white blood cells so if I've done this and it's been inflamed for a little while and now the redness is kind of going down some but I see pause and I start squeezing the pulse out is that bad what am i doing my poor body has spent all this time mounting this attack bringing all these white blood cells to the area and Here I am squeezing around and so more and more like oh the Reds come to the area to fight fight off okay that makes sense okay so now let me use the real terminology and everything I'm saying is written on this slide okay so when that first sale saw the bacteria and started calling for help it release chemicals that's what I said the first time right those chemicals have names they're called prostaglandins the called histamine if it's a beta philippi histamine they're called interleukins lots of different names depending on what cell actually secretes them the process of using chemicals to call for help is called chemo taxes chemo means chemical taxi means moving so chemotaxis the movement of chemicals through the body to call for help okay once we call for help here comes all these extra white blood cells right because extra blood flows what is the other name for white blood cell hey leukocytes the process of all your white blood cells rushing to the area to help is called leuco psychosis the leukocytes coming to the area once the leukocytes get to the area they start trying to get out right the first thing they do is go to the edge of the blood vessel another word for edge is margin so that's called margination going to the edge as they get to the edge and they start scooching actually going across the blood vessel wall into your tissue that is called dieted esis which is probably the hardest one of them to have a way remember and so that's what these four words are okay after dieted 'yes this occurs chemotaxis occurs again why if all these neutrophils are coming into the area to fight why would they start also send signals out for help what if they don't win right they need to go ahead and warn all the other cells you know we're here and we're fighting but just in case we don't win and one of them all it would take is one bacteria lead in that area right getting in your blood if they hadn't told the rest of the body they were fighting that the rest of the body wouldn't be on alert so they go ahead and send out chemicals to tell everybody else something's going on okay that makes sense yeah me too me yeah it can be any anything that goes through the epidermis can cause inflammation and have to be the nail is always the picture they put in books it can be it can be it's like I was telling up popping a pimple you pop a pimple and you forward it enough if you remember from a mt1 the root of a hair follicle goes down into the dermis so I mean you can even have inflammation occurring there and we've all probably pop something I related something that appointed it inflamed I know the women out because we just love to don't jog over the full Sun I rubbed a pop something if there's something easy popping all about it whatever you're agreeing with me those of you to think is gross I don't care it's just one of those things is there something there's got to be popped nothing grosses my walk and I can't talk to somebody that has something needs to be popped so they look at it I just can't sustain it all right so why pretty good mechanism yeah that works it works every day thousands of times a day that is all those things are going on in your body and you do not know they're happening okay but that is just the tip of the iceberg of what your immune system can do your immune system also has the adaptive part and that is a part that is a little harder to understand I missed that because it's so amazing what cells are capable of doing so we're going to approach this like I always do we're going to explain it in kind of a silly way and then correlate that with real terminology and what's really going on with are the active immune system it's even better than what we were just talking about it has a memory factor so once it sees at one time it remembers and it's ready to go even faster the second time it can respond to pretty much anything that comes in your body that's not supposed to the downside of what we're about to talk about with the adaptive immune some is they have to be presented with the problem so if I'm a t-cell ecole I think I'm floatin by me all day long and I have no idea what to do with it that's I don't know it's Nikola if I'm a teen well I want a macrophage to show it to me that's what presented me remember how about that macrophage it eats it and it sticks up he's on the surface the t-cells waiting for the macrophage to come bring it to them and say here it is and then the t-cell can go to work the b-cells are the same way they need the macrophage to break it down for them and then they can work so that's really the only con the only downside of the adaptive immune system the adaptive immune system has two parts those humoral immunity and cellular or cell mediated immunity the humoral immunity is the part of your adaptive immune system that protects you through the use of antibodies okay antibodies are made from B cells so your humoral immunity comes from your b-cells your cellular immunity does several different things but this is actually the part of your adaptive immune system that can work by actually directly killing something that's not supposed to be in your body and this is going to be accomplished by your t-cells so humoral immunity is B cells cellular immunity T cells okay so a little bit of terminology this is really the dumb part of the immune system even though we're still in the same system we're taught the same thing we need new words they use the term antigen an antigen is anything that can activate the immune system so in real life what is an antigen if I have I my jaw bacteria on board okay it's just a bacteria that dark area has a cell wall just what holds everything in there that bacteria may have a for jela okay it could have lots of different things your innate immune system will alert home out at the beginning your macrophages your neutrophils they can grab this whole thing and attack it your T cells and B cells don't respond to the whole thing okay what your T cells do is and B cells they respond to an antigen if I take just one little piece of this cell wall that's an antigen okay let's say I take another piece of this cell wall that is a different antigen if I take a little piece of the flagella that's yet another antigen okay so think about what happened when the phagocytic cell ate this bacteria when he ate today carry he broke it down into a bunch of little pieces right so should it if the t-cell and b-cell is going to use what the medication is broken down doesn't it make sense that the t-cell and b-cell only reacts to a little piece because is the t-cell and b-cell going to get the whole thing or if they go and get a little piece it's going to get a little piece okay so antigens are any small portion of a microbe that your T cells and B cells are going to respond to so what's the advantage of this once my t-cells and b-cells are activated it's not just going to be one army coming to attack this eco-lodge you're on the board army a is going to attack right here on all the e.coli on your body army B is going to come and attack all the e.coli right here army C is going to come attack right here so we end up instead of having one army of cells coming to attack the Ecola we have several armies all ultimately kill in the same cell but they're going about at different ways so they can very efficiently kill that oh that's in your body that makes sense that's one of the hardest parts of this for people to wrap their head around think about it this way if the United States decides they're going to invade another country are we going to go by ourselves nope we don't from in another country that we think has a common enemy we will make their army come with us right and both armies are going to go at the same time and fight the more armies you had are talking one thing the more likely you are going to be able to kill that one thing right so this is the way of your body mounting several attacks on the same thing that has come into your body okay so it may take this type of attack the adaptive immune system it may take it a little longer to get going right because the macrophage has first got to eat it and break it down into the little pieces but once it gets going it's much much more effective at getting rid of everything that has come into our body that's not supposed to be okay all right so let me kind of explain what this picture is on here now that I always find it that way this little red ring is supposed to represent an antigen the blue things are antibodies bonding to the antigen okay and we're going to see as we go through all this probably in our next class once the b-cells make the antibodies they're going to come back and bond okay so the antigen itself may have several types of antibodies that can bond to it where the antibody bonds that's the antigenic determinant I know it's a horse expounding term I didn't come up with it okay so how do our T cells and B cells and our macrophages know that this is a bacteria and I need to start fighting this okay we haven't even discussed that all right how I know there's got to be a way every cell in your body is what we call a self so it's Els part of yourself it's a self cell every cell in your body whether it's a red blood cell a liver cell a heart cell a skin cell every cell in your body has a protein sticking off of it that looks identical it's called the MHC marker NAC stands for major histocompatibility complex but that's just a protein that every cell in your body has the only reason you have that MHC marker is to tell the neutrophils and macrophages the T cells and B cells leave me alone I belong here I'm a self cell okay so if this e coli on the board gets in here in your body he thought will have that NHC marker he's non-self he's not supposed to be there so as soon as your macrophage says up this is non-self not supposed to be here macrophage grabs it eats it breaks it down into a bunch of little pieces of antigen then the T cells and the B cells start attacking that makes sense just terminology but you just need to be familiar with it okay so the last thing that we're going to talk about today is how do these t-cells and b-cells grow up okay I said you're born with your innate immune system right you're born with the components of your adaptive immune system but they have to mature so how does that happen all of them are made from stem cells in your bone marrow okay your T cells in your B cells are made from the same stem cell they're made as little immature lymphocytes some of them say in the bone marrow those eventually become B cells some of them travel to the thymus and they eventually become T cells that's why we call them T cells and B cells because of where they grow up okay once they're made and they travel to the correct organ they travel to assignments or stay in the bone marrow they are selected because they are challenged okay does that mean if you have chosen me to be the lead fighter in your army are you just going to choose me and say okay here you go go do what you can do probably not you're going to want to challenge me and test me to see if I'm a good enough fighter right your thymus and your bone marrow challenges your t-cells and your b-cells while in your thymus your t-cells are shown self cells if the t-cell attacks this cell what do you think we do with it we destroy it we don't want a t-cell that attacks our own body that's called an autoimmune disease that's when your immune system starts killing cells it's not supposed to okay that's considered that's considered the self tolerance test do you recognize the difference between what you're supposed to attack and what you're not supposed to attack okay the Oscar is proven that it's not going to attack something that is self something is not supposed to attack then the thymus will show through immature t-cells some antigens if they respond correctly they are then considered mature and ready and they're released into the bloodstream to go fight okay so how long do you think this process takes it takes quite a while it takes a good 3 to 6 months forth from when a child's born to make it through this process to be able to have t-cells and b-cells of their own so once a baby is born if they have a pathogen that makes it past their first and second line of defense they have absolutely nothing to fight that off if it gets in their body so what can we do to help them you breastfeed when you breastfeed your child you're giving them your antibodies because their t-cells in these so they're not going to be ready yet they have to go through all these tests and the fineness and the bone marrow before they're ready so if you breastfeed you give your child what you have and that lost them anywhere from three to six months and then at about three months they get their first shots and that's when I really their immune system really starts getting after it okay each other and die if you don't breastfeed them they're just less likely to get sick if you do okay all right do you have any questions about what we've done so far you clearly understand the first line of defense right it's just a barrier we don't want it to get past it second line of defense these cells are going to eat anything that's not supposed to be there break it down into little pieces all right inflammation is the way some of those second lines of defense cells can work together just in case we get something that makes it past the second line of defense our body has built up an army of T cells and B cells the T cells and B cells are ready to respond to the antigen the little bitty pieces of the microbe that D phagocytic cell has released what we're going to do next time is go over how those T cells and these cells can work I know I told you B cells make antibodies and T cells kill we're going to understand exactly how that works okay was it as bad as you thought it means

Channel: Mandi Parker

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Keywords: chapter, 21, part, 1

Id: sa7N42nKPqo

Length: 42min 57sec (2577 seconds)

Published: Thu Sep 20 2012