Transcript for:
Understanding the Lymphatic System and Immunity

good morning so in this video we're going to introduce the lymphatic system and immunity so we'll this video will basically take us through innate immunity which i believe is 22 4. um and then we'll do a separate video for adaptive immunity so as we look at the lymphatic system it's like there we go right we're looking at all the cells tissues and organs that are responsible for producing maintaining distributing lymphocytes right and these lymphocytes things like b cells and t cells are going to be part of what we call specific immunity right a big part of how we resist infections and disease and and we'll talk about that more in the next video but i did want to make sure we understand that right it's it's the lymphatic system because it takes care of lymphocytes right now um that being said one of the big things it does is also maintaining fluid balance in the body so it's going to return some of those interstitial fluids that we talked about with the blood vessels right so as fluid was filtered out of the capillaries we saw that quite a bit of it was reabsorbed but not all of it and so we're going to see the lymphatic system involved in returning that fluid to the cardiovascular system so we carry a fluid in this system called lymph right it's just a plasma-like fluid the what gets people is it was called plasma when it was in the blood right and then it leaks out and we call it extracellular fluid or interstitial fluid and then when it moves into these lymph vessels it's the same fluid but now we call it lymph right it's all the same thing so we'll take a look um at how that works we'll talk a little bit about these vessels and then also some of the lymph tissues and organs right so these lymphatic vessels you kind of see spread throughout the body here they are basically carrying the the lymph that interstitial fluid that we're trying to return so it's picking it up in the tissues and returning it eventually uh to a vein the nice thing about this setup right is one we get to return that excess fluid so you don't constantly just swell and swell as well it also acts as a way to transport transport lymphocytes so they can move out of the blood into the tissue back to the lymph back to the blood right they can move around it helps us we talked about this with the cardiovascular system that that ability to filter things out of the blood is what's going to make it even easier to distribute things like hormones nutrients wastes etc and this lymphatic system also helps us maintain blood volume so not only do we not want to just keep swelling but we also want to return that fluid to the cardiovascular system to maintain blood volume which then helps us maintain blood pressure we also um need to take a look they're showing on this picture as well things like the spleen and the thymus and lymph nodes and tonsils so we'll talk about these lymphatic tissues and lymphatic organs as well basically the the big difference i would say between a lymphatic tissue and an organ is the organ is actually going to have a capsule around it where the tissue is a little more diffuse and we'll see that embedded in the walls of other organs a lot of times so when we think about tissues we'll talk about the tonsils that's actually some kind of more diffuse lymphatic tissue and then things like this the spleen and the thymus are some of the lymph organs so these organs do um produce and store lymphocytes um and we'll look at that process okay so let's jump in here so here's a look i stole this from another book because here's your oh i didn't even put your picture in um i think it's still 22 too a look at what these lymphatic vessels look like particularly we're going to start out in what we call lymphatic capillary so this lymphatic capillary is not quite the same as one of the capillaries in the cardiovascular system so they tend to be larger in diameter they have very thin walls right that's a similarity and then this is kind of interesting right they actually originate as little pockets right almost like a cul-de-sac um so there's no flow through a lymphatic capillary starts basically as a dead end embedded in the tissue it is made up of endothelial cells but unlike the capillary it actually lacks a basement membrane lots of these lymphatic capillaries in places like the small intestine i mean they're spread throughout your body but in the small intestine we give them a separate name we call them lacteals we'll see a ton here in the small intestine because this is actually our only route for really absorbing lipids so lipids don't dissolve in water well they don't go into the bloodstream right away they're actually going to move through these lymphatic vessels before they enter circulation so from that capillary we would then enter a small lymphatic vessel it actually ends up being similar to a vein okay so notice things like they have valves in them um we then move on oh i also want to point out sorry before i move out on these lymphatic capillaries maybe this is the best picture to do this in um notice that the endothelial cells overlap um it kind of acts as a valve or like a one-way door so fluid can move into the lymphatic capillary but then those um endothelial cells kind of any lymph pushing back is actually going to close that little flap and that's separate from the valves right that we'll see particularly as we start moving into lymphatic vessels that are preventing backflow down this lymphatic circulation this is what happens when the lymphatic system fails so a very visual representation of this system to be able to drain fluids from from the body so this is actually a result of a parasitic infection that damages some of these lymph vessels and and is is preventing the removal of that fluid um elephantiasis is the name of this disorder okay so from those small lymphatic vessels we do start moving into some more major um lymphatic vessels don't there's a ton of them right and we don't need to know all of them but you should realize you have a lot of major lymphatic vessels that stay a little more superficial so they would be subcutaneous just deep to the skin you would find lots of these in places like mucous membranes so lining the respiratory system the digestive system urinary reproductive things like that as well as in the serous membranes so places like the pleural cavity pericardial cavity those sorts of places right we're going to remove excess fluid you also have deeper lymphatic vessels and those tend to run kind of in parallel with arteries veins nerves they the lymphatic vessels even these bigger ones they tend to have kind of this pale golden appearance and remember they're much more like veins so they kind of collapse they're pretty difficult to find um in dissection so the stuff i want to have you focus in more right is as all of these different um lymphatic vessels are are moving together and you can call them ducks as well lymphatic ducts um they're eventually basically all going to kind of um almost all fuse together so notice what they're showing you here is the upper right quadrant of the body really gets drained by this right lymphatic duct right and we actually see that right here dumping into the right subclavian vein on the left hand side of the body and i guess the right lower side of the body as well so the other three quarters of the body all of that lymph is going to come together in what's called the thoracic duct um so it's collecting everything inferior of the diaphragm and then also the upper left quadrant of the body um this is going to dump into the right thought i was gonna sneeze maybe into the right i'm sorry into the left subclavian vein right so you see that entering into this subclavian vein here now um and i will point out the the base of this thoracic duct is kind of expanded you see lots of different kind of trunks coming in here the cisterna kylie is that little expansion or sinus there so this is how we're actually returning all of that fluid to the cardiovascular system right it's going to be collected throughout the body and enters the venous system one of the nice things that happens though is before we get there we're going to go ahead and filter it we're going to screen it so the lymphatic system we said really focuses on the kind of care and provision i suppose of these lymphocytes and so we'll get into these more when we talk about adaptive immunity but remember what we're looking at here are things like b cells t cells and natural killer cells and these are going to be constantly looking for invading microorganisms so what we end up doing then is our in our lymphatic tissues and lymphatic organs we're basically going to filter and screen the lymph right as it's traveling through those lymphatic vessels so when we talk about lymphoid tissue or lymphatic tissue here we're talking basically about a connective tissue typically reticular filled with reticular fibers if you remember that from the tissue chapter so we have connective tissue that's really dominated by lymphocytes right lots of b cells t cells natural killer cells embedded in there so here we're looking at a lymphoid nodule notice it's also called a tonsil these lymphoid nodules they don't have a fibrous capsule and so this is still lymphatic tissue it's not truly an organ here so what we'll see is in the these lymphoid nodules when we see them in the respiratory lining the upper respiratory tract typically we call them a sinus we will see these very richly in any of our mucous membranes right so digest again digestive respiratory urinary reproductive a lot of times these lymphoid nodules aren't even as pronounced as what we see here in the tonsils and so what scientists have started calling it is malt mucosal associated lymphoid tissue so any of those mucous membranes might have a really rich distribution of these lymphoid nodules in particular when you get into the small intestine sometimes they refer to it as galt gut associated lymphoid tissue it's still malt but it's specifically in the gi tract and even more specifically a lot of times lining the small intestine will refer to payers patches and these are pretty obvious histologically again just deep to the mucous membrane where all this absorption is taking place remember you have lots and lots of bacteria that are inside the lumen the hole the hole there we go of the intestine and you want glucose and salts and all these things to be absorbed but you don't want those bacteria gaining access to the body and so you have this very rich distribution of malt including what we would call pears patches the appendix also falls under this a lot of people i know talk about the appendix as if it's a vestigial organ something that used to have a purpose and no longer has that purpose but it does seem that it actually has a really rich distribution of malt and so we could say it's actually part of the lymphatic system here so there's your tonsils we will look for these in lab i think with the respiratory system um typically um when people are talking about their tonsils being swollen it's actually these um i feel like they switched those around shouldn't the palatine tonsils be on the palette oh it is okay i see what we're looking here look at this picture so um here's the palette right hard palette up front soft palette in the back and the palentine tonsil um is kind of hanging down there with the uvula the pharyngeal tonsils are way up high actually up in the nasopharynx and then the lingual tonsils at the base of the tongue okay so that picture's art okay let's look at lymph nodes so lymph nodes are truly organs right they actually are contained inside of a connective tissue capsule and notice what's going on here and then this is the image from your textbook 22.6 um basically in all of our lymph nodes we have lymph being brought to the lymph node through an afferent lymphatic vessel remember affair so just like neurons afferent is is moving towards um our lymph node and then we'll see that same lymph being carried away through an efferent vessel but by then it's already been filtered and so the idea here is you're bringing the lymph through this lymph node and you're bringing it past all sorts of immune system cells so macrophages and dendritic cells dendritic cells are also arise from monocytes both of these are phagocytic cells they're great at activating adaptive immunity so bring the lymph filter it past macrophages in these lymph nodes you have tons of b cells and again not super worried that you know the exact locations of these but it's really rich in b cells in t cells um and even in antibodies okay and so if you have an infection and you feel lymph nodes getting enlarged right or sometimes and a lot of times these lymph nodes are in places like the axillary region or the inguinal region anytime those are enlarged you would think there's probably some sort of infection going on some sort of inflammatory response it can also be one of the first indications that there is cancer this is one of the place that cancer will often metastasize too anyway lymph nodes it's purifying this lymph before it reaches veins so this is actually pretty clever anything that you're collecting from the tissues you get a chance to kind of screen it the other thing that happens is these lymph nodes act as kind of an early warning system so what we'll see as we start talking more about the cells here in the lymphatic system is a lot of times they're releasing different cytokines different chemical signals and so they're able to kind of alert neighboring tissues neighboring lymph nodes so it serves as kind of an early warning system to infection so the thymus we see the thymus sitting here just above the heart i think a lot of us saw that in the cat this is also an organ it's enclosed in the capsule this is the one that we said kind of shrinks with age and the t cells develop here so it's considered part of the lymphatic system because it is hosting and helping t cells to mature we talked about it with the endocrine system because it also stim it also releases hormones um particularly thymosins which stimulate the t cells to to mature and develop so it's one of these organs you know we break the body up into these chapters like these systems are all separate but this is a really good place to remember that all of these systems are really integrated and sometimes it's not so easy to just kind of decide to put it in one box and so yeah that's basically fills roles in both the lymphatic system and the endocrine system the spleen so the spleen is another lymphatic organ it does have a capsule though it is very fragile this capsule is not particularly strong you can damage the spleen with blunt trauma particularly you know big wrecks big accidents and things like having mono which would actually enlarge the spleen in response to that infection can make it even more fragile sorry dog freaking out um so yeah having the spleen enlarged due to something like mono can make it even more fragile so this would be the classic example is like the high school football player he's contracted mono he's not supposed to play because a lesser impact could actually rupture the spleen and the spleen is a little different in that the spleen isn't filtering lymph the spleen is filtering blood it's still part of the lymphatic system because what we're going to see is as you get down kind of into the the deep histology here is that again it's housing lots and lots of lymphocytes so one of the spleen's main jobs i mean it filters blood and one of the things it's looking for is actually the older kind of worn out red blood cells ones that aren't going to actually fold very nicely and fit through capillaries and remember from the blood chapter we try to take them out of circulation before they rupture because we want to recycle those nutrients right remember the the iron is going to get sent back to the bone marrow and then the the protein portion of hemoglobin um is going to get recycled part of it it ends up as bile okay um but the spleen right has tons again of things like macrophages dendritic cells b cells t cells and so again it can initiate an immune response here there's yearbook's picture of the spleen as well and thymus we already did that okay so i did like this image i think i'm in your way down here um figure 22 9 it's kind of hard to see it's too small probably to have as a slide here but it does a really nice job of kind of showing you all these different um kind of parts of the lymphatic system right so they're trying to show you here how all these lymph vessels are going to bring the lymph through the lymph node we get it filtered we return it to the venous circulation right pointing out specifically that lymph capillaries in the small intestine are called lacteals and that is also going to come back onto the venous system we see the spleen that we just talked about filtering the blood they're showing the role here of bone marrow and this is going to be really early in the development of some of our lymphocytes so we'll look at how the b cells and t cells arise from stem cells in the bone marrow here's the thymus right some of those immature t cells actually migrate through the blood to the thymus right and they leave as mature t cells able to actually do their job and so a kind of a nice summary here okay and again all those then mature this is what this last one is showing all those mature b and t cells right they arise from bone marrow they develop either in the bone marrow or the thymus depending on which cell type and they spread out throughout the body into all these different lymphatic tissues lymph nodes lymph nodules tonsils the spleen right etc and they're able to kind of move in and out of those tissues through the bloodstream so i thought figure 22 9 was kind of a nice summary there okay so we are going to keep rolling here and we want we're going to start by looking at the innate defenses so as we move into this big idea of immunity right what we're looking for is the ability to resist disease but how this ends up happening in the body is it really gets split into two main branches the one we would call your book calls it innate immunity i tend to call it innate defense typically what we mean by immunity are these adaptive defenses right um utilizing things like b cells and t cells where we gain immunological memory where you only get sick from the same microbe once right subsequent infections don't lead to illness that's what we typically call immunity and so that would be part of this adaptive response so what i want to talk about um to wrap up section i think is 22-4 um are these innate defenses so innate defenses are non-specific they do not distinguish one type of of threat from another right so they don't care whether it's h1n1 or h3n2 influenza they can tell it's foreign and they want to go after it um so we're going to look at things in these innate defenses like physical barriers phagocytic cells like macrophages they don't care what bacteria it is they're just going to engulf it um and a whole slew of things we'll talk about some different chemicals the inflammatory response fever right all of these are innate the other thing that you should think about innate defenses so they're non-specific right they don't care what the microbe is um and they're basically things that you're born with right these don't have to like um they don't require a previous exposure to some infectious agent you just have them they're ready to go okay and again these adaptive defenses they're specific right if they've seen h1n1 before then you have immunity but if you get h3n2 influenza right we're going to have to spend some time mounting this immune response so they're specific right they protect against particular threats they require exposure right you're not just born immune to influenza h1n1 you actually have to have exposure to the that particular antigen i will also point out these adaptive defenses then are where we see the lymphocytes the b cells and the t cells right and they're wandering through tissues and we see how they might hang out um in different lymphatic tissues lymphatic organs but they're traveling moving in and out of circulation etc okay so there's a lot in here but we're just going to get through innate defenses and then i'll make a separate uh video so we can all have a break you of course can hit pause at any time okay so innate defenses again i've pulled this out of another um publication but i think this is a really nice summary of what your book is talking about so here we see a list of what like seven different innate defenses non-specific and you're born with them right so the first one would be physical barriers right actually intact skin and mucous membranes this barrier think about um how how many layers there are for example in skin right we looked at even just the epidermis the stratum corneum that superficial layer um it's all dead cells right it's not going to be a great habitat for for microbes to survive in right it's it's dry it's slightly acidic um all these things okay um it's filled they're all filled with this really difficult uh this tough protein called keratin right and that's going to help this be a very good physical barrier to microbes entering the body and then of course we have all these accessory structures if you look at different you know sweat glands that those secretions maybe in tears are keeping that mucous membrane clear you actually flush a lot of these mucous membranes urine keeps the urethra mucus membrane clear um yeah again tears there's the actual enzyme in tears called lysozyme which breaks down bacterial cell walls if you think about sweat coming out of some of these glands in the skin it's typically slightly acidic so not a great habitat for most microbes mucus that you would be producing on the mucous membranes like snot and stuff like that right it's it's trapping microbes and then it's flushing out of the body you have on the mucous membrane in the respiratory tract you have ciliated cells that actually help propel um that mucus and any microbes that have been trapped up and out of the respiratory system right instead of letting it settle down into the lungs so physical barrier-wise you're born with a bunch of defenses right from um microbes particularly i'm thinking bacteria but i suppose viruses as well from gaining entry to the body heck worms fungus whatever microbes um pathogens microbes capable of causing disease pathogens you're born with these physical defenses against pathogen entry okay the next one they're talking about here are phagocytes phagocytes are a group of cells that engulf and destroy pathogens right we have i'm in the way again we have two main categories here um actually sorry more than two um the neutrophils this is the most common white blood cell you saw this in the blood chapter and there we go again right is it blood or is it immune system it's both so neutrophils um i tend to think of these as little kamikaze pilots right because they are gonna go ahead and do phagocytosis um but and your book says that they often die after a single phagocytic event so engulfing one bacteria i've more commonly seen up to like a dozen bacteria might be engulfed but it does self-destruct so when it engulfs that microbe right it's using some gnarly chemicals things like superoxide or hydrogen peroxide right things we might classify as free radicals so it's using free radicals it's using enzymes different chemicals to actually destroy that bacteria and eventually it actually destroys itself in that process as well eosinophils again we talked about a little bit with the cardiovascular system they typically go after after multicellular parasites you can consider them a phagocytic cell but usually what they're attacking is too big to actually be engulfed and so they'll often kind of scoot up next to it and use again things like nitric oxide different enzymes to destroy those parasites the star of the phagocytic world is the macrophage right so macrophage literally means big eater um and so this phagocytic cell um is is going to um again engulf bacteria and destroy them with a variety of different enzymes um but these guys can just keep going and going they're actually much longer lived than the neutrophils so again monocyte derived right we saw them as monocytes in the in the bloodstream once they move into tissues we call them macrophages right a lot of tissues are sheltering kind of these visiting macrophages so they've moved out of the bloodstream right so they're saying some are floating around those would be the monocytes in the blood some of them become fixed a lot of times these macrophages are kind of moving in and out so if you hear people talking about the reticuloendothelial system this is this connective tissue that's really common to see macrophages kind of move in and out of um you do have some specialized um i guess monocytes like microglia if you remember those from the nervous system they're in the brain they're basically a fixed macrophage they're stuck in the brain they're not coming back out because of the blood-brain barrier um in the skin we see a series of cells called dendritic cells or langerhans cells your book probably called them dendritic cells they're embedded in the epithelium of the skin so great place right another way to kind of reinforce that physical barrier but they're all capable of moving around so they're using chemotaxis right they're actually sensing chemicals from these pathogens or sometimes from the immune system they can follow that towards the site of infection um they will then right if they're in circulation they'll actually like adhere to the capillary wall and start um crawling right they use an amoeboid movement so instead of just getting like flung right past the site of infection because you're being carried really rapidly by the bloodstream as they start sensing they're getting closer they stick to the capillaries cell walls they start crawling towards the chemical stimulant and then they use a process called diapedesis where they're able to squeeze out of the capillary between cells anyway they can engulf quite a few microbes in their lifetime oh so this is that reticuloendothelial system and this is actually a really nice image to remind us of the relationship between the blood and the lymphatic system so what they're showing you here is that capillary and how we have filtration so we see some stuff moving out and reabsorption but of course filtration is going to exceed reabsorption and so instead a bunch of that fluid ends up becoming extracellular fluid what they're pointing out is that throughout your body you have this connective tissue and white blood cells are going to be able to move in and out of that and they're calling that this reticuloendothelial system we think your book also points out that maybe we're realizing um that's not exactly true and i mean i mean it's true but it's not like a system unto itself and so they're starting to call it more like the mononuclear phagocyte system anyway again some of these things don't fit in nice little boxes nice little chapters like we want them to realize that that white blood cells can move out of the bloodstream hang out in tissues they can move back into the lymphatic system when they want to right they can just go with some of that extracellular fluid back into the lymphatics and get returned so that's this is kind of nice right they're showing extracellular fluid when you're not in the bloodstream and then once you're in the lymphatics we would call that fluid lymph okay so immunological surveillance um this is going to be conducted by cells called natural killer cells now natural killer cells are kind of um interesting because they're actually lymphocytes like if you look at the the lineage of all of our white blood cells you'll notice that natural killer cells come from a lymphoid stem cell and they're like cousins with b cells and t cells but they're involved in innate defenses right which is very different than our other lymphocytes so basically these natural killer cells um are kind of constantly circulating and we call it immunological surveillance because they're looking for the bad guys and they recognize um these foreign cells bacteria virus infected cells right so it could be your own cell that they recognize um is infected with a virus they can pick up on cancers right they're looking for these proteins and again this is non-specific so what ends up happening particularly if you think about microbial pathogens is they actually the what the natural killer cell picks up on is what's called a pamp a pathogen-associated molecular pattern so basically even though there's individual differences in all these bad guys it's like they have the same trench coat on or whatever and so um the natural killer cell is able to recognize them for that and so what they do so here we see um a natural killer cell kind of scooted up against an infected cell it's a eukaryotic cell so i'm assuming it's like a virally infected self cell um and it secretes some chemicals that are called perforins so it's like shooting little holes into the cell and once that cell membrane is um uh broken water can rush in right we lose selective permeability um it's formed these pores and the cell is going to undergo lysis so that's kind of a fun one okay um interferons so interferons um they're chemical messengers um that typically their main role is against viral infections so what they're going to do is a virally infected cell this isn't this isn't a special cell this is any of your cells once infected by a virus is going to release this chemical called an interferon and it's attempting to interfere with the viral replication and so basically it ends up alerting neighboring cells um that there's a virus right and to basically try to um [Music] batten down the hatches and keep the virus from infiltrating them as well so yeah i don't have a great picture there they help the neighbors like build a better fence right like hey there's a virus coming that was kind of what i was going for there um sometimes they're grouped with other kind of chemical defenses in the innate immune system so some of these chemicals are getting released kind of attracting phagocytes or sometimes tagging um the pathogen so that something like a macrophage comes and finds it so there's other chemicals but i guess we're just talking about interferon so um virally infected cells telling their neighbors to protect themselves um okay complement so complement is a series of proteins they're inactive they're just circulating around in the blood and they complement the activity of antibodies so they're non-specific we'll talk about them here sometimes you can actually just directly find a pathogen and attack it with complement but it's often something where an antibody has attached itself to say the outside of the bacterium and that's the signal um for complement to come in so it complements the activity of antibodies and so um two different pictures here your get myself out of the way [Music] your book um did a nice job of kind of laying out these different pathways right how this might happen and so this is where i was saying often what they're calling the classical pathway this is when the complement protein attaches to an antibody that's already kind of tagged the cell this alternative pathway is the spontaneous one where it's able to recognize a foreign microbe directly excuse me i kind of like this picture because it shows what ends up really happening i guess both of them show it but um so you have this series of circulating proteins and they're going to come and kind of arrange themselves in this nice ring in the cell membrane of the pathogen and again once you've disrupted that selective permeability of a membrane that cell is more apt to rupture in if you've taken micro um gram-negative cells if you can embed this in the outer membrane and you lose selective permeability then you're able to more easily target the cell in a a eukaryotic cell right if you lace the membrane the cell is going to explode um in our bacteria since they have a cell wall we're still going to need to do a little more activity on them anyway don't get too lost in that right it creates what's called the membrane attack complex it creates this pore in a cell membrane which is leading to lysis okay the inflammatory response this is a super important um innate defense and i say is super important because we've all experienced inflammation right we know a little more about it and we're starting to find actually quite a few diseases where chronic inflammation is problematic so it's really important to kind of understand what this process is so the idea of inflammation is actually to limit the spread of infection and so what you end up seeing right if you think about signs and symptoms right signs are objective things you can actually see symptoms are something your patient reports so i realize this is all in latin here right but rubor is redness okay you would actually see that it's a really nice sign of inflammation color is temperature or heat and so probably heat is a better translation um and so you could feel that right like uh a doctor might actually right you've got a inflamed finger so they might actually feel it to see if it feels warmer than other fingers um two more that's gonna just be the swelling or edema also very visible dolor is pain that would be a symptom right so the patient is reporting pain and the pain is actually useful as well right because that often is what limits the function like right you don't want it to hurt more so you stop using it and so that's trying to protect this injured area okay let's look at the actual process here so classic example so we're stepping on a rusty nail here it's covered in bacteria so now we have bacteria in this wound now before the inflammatory response your initial reaction is to stop bleeding right hemostasis and so what we see is this initial vasoconstriction but then as we kind of pick up on our actual inflammatory response what we're going to see is that mast cells here we go mast cells in the area remember these are related to basophils mast cells release they're saying chemical mediators histamine right mast cells release histamine and also heparin so histamine is going to cause vasodilation and it also causes the capillaries to become leakier right it opens up remember capillaries are endothelial cells they're actually held together by tight junctions to make sure stuff's just not leaking out all the time if you're in a continuous capillary anyway um so histamine actually kind of relaxes that makes it easier for things like white blood cells right here we see neutrophils macrophages entering the site of infection heparin is a blood thinner so it's going to help increase blood flow to the area as does vasodilation right so we open up this blood vessel and we are going to help bring more of those white blood cells past the area of infection right so they can smell the chemotatic factors and move towards the site of infection um yep so the other thing that you see kind of leaking out of these capillaries or blood vessels is plasma so this is going to be why we start actually um getting edema so as that fluid is leaking out it's filling the tissue you actually are able you're using that to bring fibrinogen to the area and so you can um you can split that you can make fibrin right remember fibrin from blood clotting you can actually do that in this area of infection and so it kind of helps wall off the area so that the bacteria can't just spread through the tissue so there's actually a lot going on here in this inflammatory response plus they're pointing out here remember passes or purulent exudate would be another term pus is going to be all that plasma right all the fluid all the dead neutrophils that were kamikaze pilots dead bacteria all those things all right and then last but not least in our innate defenses is fever not that kind of fever that kind of fever right so an increased body temperature so often you'll see um in our textbook body temperature being listed in celsius so 37 degrees celsius is considered a normal body temperature um basically anything higher than 37.2 or 99 degrees fahrenheit you're probably more familiar with is considered a fever okay so fever this increased body temperature is actually set up the hypothalamus in the brain is basically acting as the thermostat for the body so you can you have a series of chemicals called pyrogens that actually induce this fever so pyrogens could be um from the pathogen itself right something we respond to and kind of turn up the temperature or some of your other white blood cells can actually release we'd call those endogenous pyrogens pyrogens that we made ourselves but also to stimulate the hypothalamus to go ahead and up the body temperature and one of the things to think about is like why would we do this right um some of it is to probably inhibit microbial growth it's you're not going to be able to heat up enough to just straight up like denature the proteins and kill the pathogen without causing a lot of damage in yourself right so sometimes a fever can get too high you start hallucinating you're denaturing your own proteins that's bad okay so you're typically not using fever to truly kill a microbe but if you can make the temperature warm enough that it's not in its optimal growth temperature its reproductive rate will slow down so you can kind of slow down the growth of that microbe and at the same time you're actually upping the metabolic rate in your own cells so you can get macrophages and lymphocytes and all these white blood cells to actually work a little bit faster okay so those are our innate defenses again non-specific doesn't care what the microbe is and these are things that you're born with right you don't have to have a previous exposure in order to have that reaction all right i'm going to end this one here take a quick break and then we will talk about the adaptive defenses