body defenses how do you protect yourself you can't blame the organisms everything wants to be inside your body because it's a nice warm happy cozy little place you're gonna feed it you're gonna give it water you're gonna keep a stable body temperature who wouldn't want to live there so we can't really blame them for wanting to be there but that means we have to constantly defend ourselves from these things that want to invade us whether it's a bacteria whether it's a worm whether it's a virus whether it's a fungus they all want to come home sweet home those of you that have had microbiology will be familiar with a lot of this this is immunology the study of a host specific defense to a pathogen a pathogen is a disease-causing organism so technically viruses aren't pathogens because viruses are not alive when you get sick with a virus you can't take an antibiotic right because antibiotics are anti life so that's not going to work on something that's not alive but for our purposes you can think of viruses as things you're obviously trying to defend your body from they're just not technically pathogens so this is you know a whole branch of science you could spend years studying immune ology we're just gonna hit the high points are we defending ourselves against we're defending ourselves against antigens so we talked about antigens and antibodies in lab when we talked about blood typing remember antigens are the things that our bodies recognize as either being US or foreign matter so bacteria viruses protists fungus anything parasitic worms anything they're gonna have their own antigens as well so we need to be able to recognize those as being foreign they're usually made of proteins and we recognize them as being the enemy so we can either protect ourselves in very general ways against all antigens which we would say is nonspecific like in your house you don't really care if you put up a fence you don't really care if you're trying to keep your neighbors out if you're trying to keep your neighbors dogs if you're trying to keep deer if you're trying to keep rabbits the fence is just keeping everything out or we can protect ourselves selectively against a specific antigen which would then we would say would be specific defense this would be like spraying raid to keep out cockroaches so you can say okay here's my fence to keep out everything I don't care what it is non-specifically or specific that targets one particular thing so your immune system or your fat or your lymphatic system is incredibly impressive and it's designed to defend yourself against constant barrage of viruses bacteria fungus toxins and parasites these things want in so it's kind of like your house if you're constantly trying to keep mice out of your house well if you went on vacation for two weeks you'd probably come back and there be some mice in your house you have to constantly defend right you can't spray raid once you have to keep spraying it you can't set a mousetrap once you usually have to keep setting it you have to keep setting your alarm on your house or keeping your fence up so these are things you as soon as you stop as soon as you lower your defenses you're gonna get invaded in this case it's by something that can make you very sick your immune system is a very powerful thing that you can see in action constantly you've noticed it when you get a cut as soon as you get a cut if you remember the skin from A&P one the epidermis that top layer is designed to keep stuff out well if you cut yourself you're getting into that middle layer the dermis where there's tons of blood vessels so now you've given a perfect opportunity for the invaders to get into your bloodstream and remember if things get into your bloodstream in one minute they're everywhere they want to be like visa you can see your immune system working when you get a bug bite so mosquito bites when you get that itchy bump it's a sign that your immune system is doing its job it's trying to counteract whatever toxins potentially those insects bring into your body we can see our immune system fail when you get a cold or a flu usually from a child Oh children they're just little petri dishes of disease and they don't cover their mouths when they cough I know a lot of adults that don't do that either but if you look at this picture of this virus it's like flu viruses they have the you know they have like similar makeup as far as if you look at their cell membrane they're covered in antigens and so when we see these antigens on a foreign bacteria or on a virus our body doesn't you know recognize those and says oh I know that that's not you know human but it doesn't have a weapon it's kind of like the first time you know you get if you're positive and I'm sorry if you're negative and somebody gives you positive blood it's like you know it's not your blood but you can't really defend yourself so that's why you have to get sick when you get sick and have all those nasty cold and flu symptoms your body is building those antibodies to attack this virus or bacteria when you eat you're taking in hundreds of microbes you can't help but have bacteria on your food we don't live in a vacuum so as soon as your food is exposed to the air things are gonna land on it but ideally your immune system takes them out but food poisoning oh good times if you've ever had food poisoning for me it was Walmart pizza fall 2010 I don't know if I didn't cook it long enough or I don't know if Walmart didn't hold it at the right temperature but I threw up every 20 minutes for like 6 hours it was the longest night of my life I like prayed for death and so that was a situation where the food that I consumed the bacteria had grown to like very scary numbers so like most the time when you eat your stomach acid chews it up and you've got no problems but food poisoning if you leave like potato salad out at a picnic too long you're gonna be in some trouble allergies allergies our assignment or immune system is hyper aggressive it's working too intensely so things like dust or cat dander we shouldn't be allergic to we shouldn't be allergic to plant pollen these are things that are in our natural environment but if you're allergic to those it just means that your immune system is overreacting after surgery if you've had a blood transfusion or an organ transplant your own immune system might try to fight that new tissue out of your body so oftentimes after a organ transplant they'll put you on immunosuppressant drugs these are drugs that are actually putting the kibosh on your immune system temporarily to keep you from fighting those foreign tissues out of your body obviously death is bad the end game of all of your organ systems is to keep you alive but your immune system kind of has a special role in that because obviously this guy is protecting you from all the things that are bombarding your body and now have free access so when you die everything just gets on in there because it's just like if you abandon your house it won't take very long for mice to move in and spiders to move in and everything if there's nothing keeping them out so decomposition if you've ever seen kind of an animal carcass on the side of the road I love the word carcass like breaking down that's doing that because of smaller animals tearing it apart and also bacteria and molds breaking it down our body while we're alive keeps those things out but when you're dead it's a free-for-all while you're alive there's other diseases that affect your immune system that are called autoimmune diseases and these we've kind of mentioned off and on like an A&P 1 we had rheumatoid arthritis these are very very in Graves disease for the thyroid gland this semester but these are very dangerous because what are you supposed to do you can't shut off your immune system because then you're gonna get like every cold and flu virus so these are difficult to treat because it's your own defense attacking yourself instead of looking for the enemy but your immune system has a lot of work to do your body has to recognize over a hundred million antigens so antigens in this case is what our immune response is going to be a result of so there's two different classes bacteria versus viruses now of course there's worms and other things that can make us sick but we're gonna focus on the two main things getting a bacterial disease or a viral disease well we look at it from the bacteria's perspective or the viruses perspective there's two different goals here when you take micro they give you a petri dish and you streak it and you grow little tiny colonies of bacteria that's a bacterias goal a bacterias goal is to eat and reproduce whereas a virus's goal is to basically convince yourselves to do their reproduction for them viruses are not alive they can't do their reproduction for them so they make your cells do it I often think of this as like a washing machine factory gets told they have to make tanks during wartime so basically the military hijacks that company and says oh we need you to make these things for us viruses take over our cells and say make more viruses for me remember there's two ways to defend yourself non-specifically where you say I don't care what pathogen it is I just don't want it or specific where you develop immunity so specific defense is immunity if I get a polio vaccine that does not protect me from the flu that's why you have to get a new flu shot every year because there's different strains of the flu so this is very specific to one agent if you think of your body as a country that's being invaded you have lots of waves of Defense so the first line part of that first line of defense is a healthy skin so we saw this in a in p1 how the epidermis has several several layers of that stratified squamous epithelium on the outer parts all dead and keratinized and crusty that keeps a lot of stuff out it's hard for a bacteria to infiltrate your dermis because it would have to get through all of those cell layers the cells are also very tightly packed together so again it's harder for bacteria to work their way in between the pH of your skin is between a 4 and a 5 which is slightly acidic your sweat can even get down to a 3 which is the acidity of wine of course I know that off the top of my head the point is when you take Micro a lot of bacteria want to be around a pH of 7 so if they land on your skin they're not necessarily happy in that environment it may even kill them or at least protect prevent them from reproducing and taking over your skin is very salty remember tonicity hypertonic and hypotonic everybody's favorite thing well a salt environment is gonna draw the water out of cells so for bacteria lands in a salty environment it sucks its water out and kills it however there are lots of bacteria that really likes salt staff loves salt 80% of the bacteria on your skin is Staphylococcus epidermis it loves the sole lysozymes we saw those when we talked about tears remember lysozymes were the chemicals that were in your tears that attack bacteria because they attack cell walls and this is a beautiful thing a lysozyme because you could be bathing in lysozymes and it's not going to hurt your tissues because you don't have cell walls vasilia those are those little tiny hairs so these are lining your trachea and so your trachea is your windpipe it can't help but be kind of exposed to the outside world because you have to breathe well you have these little hairs that catch stuff and then if you remember from a mp1 those goblet cells that make the mucus and then the mucus elevator kind of pushes things either up and out where you either spit it on the sidewalk like a gross person or you swallow it which is kind of gross too continuing on with the first line of defense we also have our mucous membranes so when you breathe you have to breathe right you're gonna have to breathe in that air from the outside world that may have pathogens in it well you have tons and tons of mucous membranes in your mouth your nose your eyes and your stomach to trap these microbes so it goes back to those goblet cells making this mucus mucus is your buddy mucus is your friend it should be nice and clear and sticky so that way you can catch these things you can either blow your nose or cough it up or you can swallow it and it goes to your stomach where the stomach acid chews it up so we saw this one before already the eyes those lacrimal glands making those tears so that's gonna flush a lot of things off the surface of the eye because as you walk around you have to leave your eyes open right otherwise what's the point of having eyes so we need to be able to wash that bacteria and move it into the nose ultimately to the stomach we also have the lysozymes and those cheer tears to help tear up those bacteria when we get to the stomach the stomach has a pH range between 1 and 3 hydrochloric acid is a very very powerful acid we need this to chew up all the dirty stuff that we bring into our body and into our mucous membranes but we also need our stomach to be acidic to help us break down proteins when we get to the digestive chapter still with the first time first line of defense your body is covered with bacteria so these are what we call our normal flora our normal microbes your digestive tract your vagina if you have one these are very important places for these microbes so the fact that you're covered with the home team advantage means there's a lot less space and a lot less food for non normal microbes so things that are trying to invade your body they're gonna have to compete for space they're gonna have to compete for food so the bacteria that live in our bodies we need them so we call this a mutualistic relationship you only really have three choices you have a relationship where you don't get anything out of it those are very very rare because why even have them we call that a commensal relationship which you don't have to know the two main like most common relationships are parasitic where one partner benefits and one is harmed unfortunately a lot of my high school boyfriend's mutualistic I have with my husband where we both gain from the relationship so mutualistic relationships are the most healthy and in nature the most beneficial the bacteria gets something out of it we get something out of it so these are this this is our home team advantage and so when you use antibacterial soap unfortunately antibacterial soap targets bacteria it doesn't know the difference between good bacteria and bad bacteria it just kills bacteria so antibacterial hand soap is probably okay but you never ever ever want to use antibacterial body wash especially on the vagina because that good bacteria is there which helps keep the candida fungus which causes yeast infections helps keeps it keep its numbers down so the digestive tract if you've ever been ant on antibiotics for a long time it usually causes diarrhea good times but it's because you're killing all of the good bacteria inside your body to visualize how much good at bacteria is inside your body the majority of fecal matter is dead eco life so that shows how much e.coli is in your intestines and these bacteria are in there doing a lot of things for us they're helping us digest which we'll see when we get to the digestive trap chapter and they're also making vitamins for us but if you take antibiotics again it's taking out the the bad bacteria but as well as you're good and it takes a while to really stablish that bacteria back to normal numbers you're good guys anyway the second line of defense so now you've been invaded so now things are in your bloodstream you have to use your macrophages so those big phagocytes are cruising around gobbling up they're gobbling up dead cells they're gobbling up bacteria they're gobbling up viruses but this is now an internal battle another component to the internal battle is fever so your fever when you cut yourself you can feel how that localized injury gets really really hot overall we maintain a body temperature this is regulated by your hypothalamus so your hypothalamus is like your thermostat has a set point so you ever noticed that when you get sick you kind of sometimes oscillate between hot and cold so you'll get the sweats and then you're freezing you get hot and then you're freezing it just goes back and forth this is caused by a protein and you do not need to know this detail but this protein is called interleukin and he affects your hypothalamus but the goal is to like confuse whatever's invading your body so that way most bacteria when they enter your body want to be at ninety seven four or 98.6 so if you drop to ninety seven they're not happy if you go up to 103 they're not happy so your body kind of yang yang's back and forth to try to keep the foreign invaders kind of off off their game inflamation a part of that fever response I was getting at that when you cut yourself you can feel the heat you can kind of feel it throbbing so inflammation sucks which is why unfortunately we treat inflammation we'll spend more time in the next lecture on the inflammation response and how important it is but just in general right now when something is inflamed like a hangnail the swelling traps microbes our goal is to kind of wall off the microbes and keep them from spreading but when we get swelling it's going to be very tender and painful because you're pushing on all of those nerves the redness is due to the fact that your bloodstream sends a lot of blood to the injury site so that way there's platelets if you need to clot and there's white blood cells to kind of gobble up any invaders like bacteria and also oxygen proteins sugar so that way you can repair the injury so another result then is heat and that hopefully is going to kill the kill the microbes that entered your body through that injury site or at least prevent them from reproducing