we finished with the lymphatic system by discussing secondary lymphatic organs and some of the immune cells in your body and we should first think back to what primary lymphatic organs are and those are where lymphocytes mature and develop so the red bone marrow and thymus are where the b-cells and t-cells respectively mature and develop and then those cells can migrate to other places in your body like lymph nodes secondary lymphatic organs like lymph nodes are where you mount an immune defense and so they are spread throughout your body in different places but if we look at our list here we'll see it includes the spleen the lymph nodes and then some structures that we call malts malts our mucosa associated lymphoid tissues and the key term here is mucosa we're saying that mucusy regions like your oral cavity and esophagus stomach and intestines those mucusy areas have lymphatic tissue embedded in the walls and so we'll look at some of the malts specifically the tonsils highers patches and the appendix so spleen first it is the largest lymphatic organ after all it's found in your upper left abdominal pelvic quadrant and it has several functions one is that it's a blood reservoir it holds about a cup of blood which doesn't seem like much but I don't know that I've had an injury bad enough to bleed out that much blood so in that event the spleen spleen would be able to release that much blood to help keep your blood pressure constant and to keep your cells oxygenated the spleen also stores the broken down products from all of the red blood cells that it actually chews up but it'll store away stuff like iron and platelets and things that can be reused later and when you were a fetus the red blood cells in your body were actually made by the spleen those are great functions but let's talk specifically about as a part of the immune system what does the Redbook the spleen contribute and there's really two main regions of the spleen that we'll discuss red pulp and white pulp white pulp are these little spherical nodules little balls of white pulp and they sit embedded within the red pulp so the spleen is mostly red pulp with isolated areas of white pulp so when you think about red pulp think about red blood cells because it's in the red blood the red pulp that old red blood cells are chewed up and broken down and dealt with remember we learned that two million red blood cells per second are dying and being replaced so the spleen has helped from the liver but the spleen is really a big site of hemolysis breaking down those red blood cells and the way it does it is pretty interesting the red blood cells have to squeeze through these windy sinusoidal passageways to get through the spleen and if they aren't flexible enough anymore to make it through they are destroyed by macrophages these big eater cells that can engulf the red blood cells and tear them apart in the white pulp is where we have white blood cells we're not going to chew up old white blood cells here but instead these white blood cells they hang out around central arteries and watch the blood as it moves through they monitor the blood for pathogens so those are two major functions of the spleen take place in the red pulp and white pool what about these lymph nodes well there are these little oval-shaped capsules less than an inch in size and are hanging out along your lymphatic vessels so as lymph arrives at these nodes it gets filtered and then it exits the news you have them throughout your body you've got five or 600 lymph nodes but many of them are clustered in certain places you have a cervical cluster an axillary cluster and then pelvic and inguinal clusters in all cases they operate the same lymph arrives through a fferent vessels pay for arriving and then usually they'll just be one efferent leaf or exit vessel so the lymph kind of backs up inside of these lymph nodes because of that and as it's in there it will move through both the cortex the outer part and the medulla of the lymph node and in the cortex you'll have a bunch of lymphatic cells and in the medulla you'll have even more different types of lymphatic cells and their goal is to monitor the lymph to fight any infections that are found whether it be a virus or bacterial infection and to attack any cancer cells that may be found lymph nodes are pretty important pretty handy we mentioned before lymph adenopathy the swelling of the lymph nodes in response to some infection or immune response and lymphoma you may have heard of like Hodgkin's and non-hodgkins lymphoma that's the cancer of the lymph nodes because cancer cells can ride around in the lymph the lymph nodes also are sometimes biopsy to check for signs of cancer like lymph nodes in the axillary region may be biopsied to look for signs of breast cancer because as the lymph leaves the breast it would go into the lymph nodes here's a quick histological look at a lymph node so you can see all these little spherical structures are found primarily in the outer cortex of the lymph node those are where these immune cells are proliferating okay let's do our malts in these mucusy regions of your body you tend to have chunks of lymphatic tissue including your tonsils and you have four sets although only three are commonly discussed one set is the pharyngeal tonsils those are up in the upper region of your throat and your pharynx and they're sometimes called adenoids you also have Palatine tonsils and those are the ones you can more easily see if you open up your mouth and say ah they're in the back of your oral cavity you also have tonsils under your tongue lingual tonsils and so those are the kind of the three most often known about or discussed or considered types of tonsils there are also these tiny little tubal tonsils and those sit next to the opening of the auditory tube also known as the eustachian tube which you may recall drains the mucous from your middle ear so if you were to have an ear infection or some bacteria that we're starting to live in your middle ear they might get drained away on that mucus but now they're in your in your throat what are you gonna do with them well they'll be these little tonsils next to that opening to kill that bacteria as it drains out of your middle ear so those are your tubal tonsils tonsils are pretty cool they're not these round little balls they actually have like all these spiky indentations in them and those are called tonsillar crypts and the goal is to actually to trap some stuff in there you wanna trap maybe bits of saliva or food and that will allow the tonsils to do their job to do immune surveillance of the respiratory passageway you have a lot of food but also air moving through and past these tonsils they can trap some of the stuff see what's out there and mounting an immune response lots of things can go wrong with tonsils as this image shows partially stemming from the fact that these tonsillar crypts could trap some bacteria and then an inflammation response could seal the bacteria in there now you have no oxygen and nothing to clean that area out and you could get a bacterial infection or tonsil stones or other console itis disease it's grace another month is called the peyer's patch these are about one-inch follicles so little spherical structures in the walls of the small intestine especially the later small intestine called the ileum and just like the tonsils are doing respiratory immune surveillance the peyer's patches are doing intestinal immune surveillance trying to trap monitor pathogens and destroy anything they find the other thing peyer's patches do is make sure that some of the bacteria that live in your guts and that help you don't go and try to help you somewhere else so like for example we have ecoli in our GI tract we need it it helps us make vitamin K for example but that doesn't mean you want your equal I taken a cruise and going to explore other parts of your body so these peyer's patches line the walls of the intestines keep an eye on what's going past and also try to make sure we keep those eco equal eye inside of us and I have a few e.coli pictures in here just remind us here's some happiiy coli helping us or our friends symbiotic bacteria here's one being attacked by viruses inside a human host you know that's our pal you don't want those viruses attacking your equal light so although we tend to think about ecoli ending up on our salad bars do you remember they are essential for our survival and our last malt is our appendix this is a blind pouch on the end of our large intestine we used to think that it was vestigial it had no purpose anymore but in fact there is chunks of lymphatic tissue embedded in the walls of the Appendix that helps with intestinal immune surveillance again trying to trap and monitor pathogens and destroy anything that are found so if you've had your appendix out you may wonder well is my immune system now immuno compromised and the answer is yeah technically like the same way that if you've had a tonsil or tonsils removed you are missing a little bit of your immune system there as well in general there are some very very specific strains of Clostridium that people without their appendix can get but overall is a pretty minor contributor to your immune system I probably wouldn't want to have like my appendix out and my tonsils in my spleen although some people do but just the appendix in general there's not a massive immuno compromised ation to the body but one cool thing the appendix does is that as food and leftover waste move through your intestines you could potentially one day have some type of intestinal infection and the body's response to help you get over that infection would be to flesh everything out of your intestines meaning to have diarrhea to carry away all those bad bacteria to flush them out but remember you have good bacteria too and you don't want to flush all that out as well so the appendix serves as a little you know a little dead end where you can have some of your happy bacteria still surviving and after everything else gets flushed out you can repopulate your GI tract afterwards from the appendix probiotics or something could potentially also help with that but this is like nature's probiotic and of course no discussion of the appendix is complete without mentioning the risk of appendicitis where perhaps the opening to the appendix somehow it gets blocked its obstructed and you can get some fluid buildup in there you can get you she Mia so a lack of delivery of oxygen and now you'll have these anaerobic bacteria happy that there's no oxygen and they'll start to grow and parts of the tissue can start to die off through necrosis because there's no oxygen and their appendix will swell and you don't want that thing exploding inside of you because of the dead tissue because of the bacteria taking over so these emergency appendectomy x' are trying to remove the appendix before it bursts you have a lot of secondary infection risk this is a really bad looking appendix studied with the sonogram I don't see anything wrong it looks fine to me but if you're in to sonography there are lots of websites that will train you on how to tell what at normal appendix versus a inflamed appendix look like and that's just one example in that picture from the web ok let's talk briefly about some of the lymphatic cells in your body we've already mentioned these or at least a few of these T cells remember become immuno competent become mature in the thymus so t4 thymus and they provide what's called cell mediated immunity meaning the cells go around and like fight other cells that they find and they can fight a lot of different types of pathogens and including cancerous cells so they are your major portion of your immune system cell mediated immunity other cells like buh buh buh B cells remember they mature in the buh-buh-buh-buh bone marrow and they make anti buh-buh-buh bodies so antibodies can go out they can mark pathogens for destruction they can even like code viruses and stuff to make them unable to infect your cells NK cells are more rare they're called natural killer cells and they are conducting what's called immune surveillance so they are monitoring your own cells for infection maybe the infection of a virus or maybe a mutation has caused the cells to become cancerous so in either case they're really focused on your own body cells in destroying your cells if they get taken over by the way they're called natural killer cells not because they attack your own cells your very nature but because they don't have to go to the nun and I don't have a joke for that right there's no organ that starts with n where they go to mature they are natural killers they already know what to do they don't have to go somewhere to be trained so that's where their name comes from so here's a slide that you can look at later if you want that just gives a little bit more detail on these three types of cells but we should also mention that you can read a comic book for an even more soft introduction to those three types of cells and here's just a peek at a comic called viral attack it's very short but you can see here an epithelial cell being infected by virus and calling for help and read about the immune response one more special immune cell we should mention is macrophage these are these large eater cells and I like to say that they have a present for the T cells and the joke here is we call macrophages a PCS for antigen presenting cells so they're going to present something to the T cells here's the story macrophages will wander around and eat stuff up so let's say they eat up a bacterium they will then stick that pathogen inside a phagosome a little vesicle and then they'll send over a little vesicle full of digestive enzymes called the lysosome and they will use enzymes to degrade that pathogen so they break it down into a bunch of tiny pieces but then instead of just dumping out the waste product they'll save some of those fragments some of these antigens and they will present them on their own cellular surface then key cells can come cruising over and check out what the macrophage has encountered right because maybe this macrophage has been out wandering around and picked up a few different types of antigens now the t-cell gets an alert hey this stuff is out there we should do something about and then yeah the macrophage will dump out the rest of the waste products through exocytosis so that's just a tiny little glimpse into the immune cells of the immune system if you ever have a chance to take an immunology course I highly recommend it very interesting stuff going on you will at least learn a bit more about the immune system in Physiology but for now that's the end of the lymphatic system