all right in this first video in chapter 16 i'd kind of like to introduce the native immune system and immunology in general and then talk about our first lines of defenses in our immune system so a large part of our immune system is inborn in terms of being inborn i mean that you have no exposures are necessary and as you are well aware um a lot of our immune system or i should say a component of our immune system is actually devoted to developing immunity to exposures um so we'll learn those exposures and hopefully develop some type of memory against that exposure so there's kind of a generalized difference between the innate and adaptive immune system um your book breaks this up into chapter 16 and 17 respectively um one of the things about your innate immune system is it stays the same so unlike the adaptive immune system where i'm learning something for and every time i see it it may have the ability to improve my immune responses that wouldn't be true of the native immune system um immunity means the ability to fight off disease i like that definition from your textbook in this day and age because immunity doesn't mean you will not get the disease it just means your body has ability to fight it off if you have no immunity then we would say that you're susceptible to disease all right so now that we have that out of the way um kind of this introductory material let's talk about the first line of defense of your innate immune system again that you're born with and that would be barriers in your immune system and again this is stuff that i just don't think people typically think as being part of your immune system that are terribly important so one barrier within your innate immune system are things that are physical or physical barriers physical barriers either try to keep things out or will push out so examples that we could come up with in your body a very very critically important physical barrier in your body would be your skin right just the way that it's stratified the way that it grows the outer layers being dead and keratinized provides a very good barrier to preventing things from getting in the fact that you make tears and you have functional tissues and a lacrimal apparatus around your eyes that keeps things out of your eyes and keeps microorganisms out of your eyes could be considered a physical barrier i kind of don't like this but your book talks about it saliva could be considered a physical barrier the reason i don't like it is a lot of the reason that we make salivas in response to food kind of preparing for your mouth for the sensation or getting a sense that you're going to eat and getting ready to lubricate your food through producing saliva but this also has the ability to wash microorganisms off your teeth so it would be considered part or a physical barrier too mucous membranes or just mucus in general could be considered a physical barrier i think a really good example is in your upper respiratory tract trapping things that might otherwise get into your lungs and then your ciliary escalator pushing that mucus out of your respiratory tract and then either out of your mouth or um your trachea um the other ones that are here um urine would actually be considered a physical barrier in the fact that you produce it and you push it away from your body or out of your body and so that would be rinsing your epithelia of your genitals off and pushing any bacteria on that skin away from the bladder where it might cause disease so those are reasonably easy and straightforward and things you probably are very well aware of but don't think about as part of your immune system another conceptual type of barrier can be chemical so things that are chemical in nature tend to destroy or kill right that would be a little bit different than pushing out um because now i'm having some activity against the um either the infectious agent or the foreign agent that's trying to enter my body my favorite example of a chemical barrier would be stomach acid remember if i'm in the stomach in the acid i'm not technically in the tissues of your body yet and in nutrition you talk about the fact that this part of the thing that this does is it attempts to sterilize your food so that would be a chemical barrier preventing things from getting into my body you could also have sweat and then the fact that your sweat is salty so that salt that would accumulate on your skin could be antimicrobial the oil that's in your skin and the earwax that's in your ears are antimicrobial the oil is anti-fungal and the ear wax is mildly acidic so those things would be chemical in nature and then the other thing that your book talks about again are enzymes in your saliva so again that's part of the reason why i struggle with that a little bit being a physical barrier and one of these enzymes we talked about in your saliva in chapter four um is called lysozyme when we talked about that in chapter four we said that lysozyme was good at degrading peptidoglycan and specifically in killing korean positive bacteria so you have this enzymatic defense in your saliva that is trying to destroy bacteria before it even enters the tissues of your body all right the last thing that your book considers part of your innate immune system and i completely agree it's just kind of new in terms of microbiological thinking would be normal bacteria in your body and really the large component of this is just the fact that they're occupying space and i know we've talked about that a few times in this class i mean if i have a space like your skin and that space is filled with normal bacteria maybe green's not the best color for bacteria on your skin because it wouldn't be photosynthetic but if i occupy that entire space i have no room for pathogenic growth right so another great example of this would be in your intestines one of the advantages of having bacteria colonizing your intestines is i can omit or include that pathogenic bacterial growth one really good example of this gone wrong is with c diff and some of you have written about c diff most patients that have c diff have gone through rigorous antibiotic treatments for another infection that will in a lot of ways sterilize the gut and then once i've sterilized the gut through that antibiotic treatment now an opportunistic pathogen like c diff can take over and colonize the gut so that would be a big advantage of normal bacteria just in terms of being a barrier to preventing disease for opportunistic pathogens all right so that's all i have for this video i'm going to try to keep some of these in this chapter kind of short so i'll zoom out of that and i'll see you next time you