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>>Dr. Ketchum: Now we’re going to start the immune system. And so what I want you
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to think about first off is, “Well what is immunity?” So humans demonstrate immunity
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by possessing tissues that are capable of recognizing and protecting them against non-self
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invaders. Short and sweet—your immune system is there to defend your body from foreign
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invaders. Those foreign invaders come in all shapes and sizes and varieties. So let’s
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look at what the targets are for the immune system. In other words, who are the foreign
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invaders? Some of the targets are pathogens, and these pathogens can be viral, bacterial,
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like staphylococcus. They can be actual parasites, like for example tapeworms, roundworms. The
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targets may be fungi or even protozoa, which some of you may be more familiar with protist.
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Protist is a newer term that we’re using these days.
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Now there are also other targets for your immune system. So worn out cells. As cells
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in our body start to wear out and die, they are now targets for the immune system. Because
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when it’s wearing out and dying, it’s more likely to start dysfunctioning and can
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result in cancerous cells, can cause tumors, and all sorts of things. So you want to kill
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the worn out, dying cells. The other thing that the immune system is going to target
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are mutant cells. These are abnormal cells in the body, and then also cellular debris.
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So when you think about cellular debris, think in terms of if you’re going to break down
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a cell and the debris that’s associated with that cell once it’s broken down. Okay,
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so let’s take a look at some of these pathogens here. So we have bacillus—this is a bacteria.
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And these are just examples, so you do not have to memorize these. Fasciola, these are
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some flukes, these are flatworms that you might inquire by eating undercooked fish for
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example. This taenia solium, which is a tapeworm, and specifically this is called
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a pork tapeworm because you will become infected with a pork tapeworm if you eat undercooked
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pork; so it’s really important to cook your meat thoroughly. There’s also a tapeworm
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called the beef tapeworm. And the beef tapeworm you get from eating undercooked beef. So for
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those of you that eat your steak rare? Careful, beef tapeworms can reside in your small intestine
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for quite some time, and then when they die, then the entire tapeworm can be released all
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at once when they die. And they can be up to eight, 10, 20 feet long, okay? So beef
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tapeworms are really long.
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Then there’s trichomonas vaginalis—trichomonas vaginalis. So this is a protist, and based
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on the name you would think that this pathogen only affects females. That’s not true. Men
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can actually get trichomonas vaginalis by coming into contact with females. So during
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sexual contact—so trichomonas vaginalis is actually considered a sexually-transmitted
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disease, an STD; so men can get trichomonas vaginalis. Then there’s clostridium difficille.
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Clostridium difficile is a bacteria that literally wreaks havoc in nursering homes, and what it
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does to the elderly is it gives them profuse diarrhea, and, and the diarrhea is so watery
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that the elderly people tend to dehydrate very quickly and sometimes they do succumb
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to a clostridium difficile infection. Then there’s giardia. Giardia is the cutest little
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parasite on the planet. So when you look at this little guy here, he looks like a happy
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little thing. He looks like he’s smiling and like he’s got big old glasses on like
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Steve Erkle or something. This protozoa—and this one wont kill you—but this is what
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you call “Beaver Fever.” So if you drink contaminated water that a beaver has pooped
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in, the beaver pooped giardia into the water and now you drink the water. So if you like
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to go hiking and camping then it’s a really good idea to filter your pond water.
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All right, then there’s plasmodium. Plasmodium is the protist that causes malaria, and I
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know a lot of you have heard about malaria and how many children that it kills every
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minute of the day. And malaria is the number one killer of children and adults in terms
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of arthropod vector-born diseases.
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So those are the examples of just various targets for the immune system. We have
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all of these cells, then, in our body that have to amount an immune response. And here’s
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the anatomy of the immune system. We’re going to break this down into two components:
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the leukocytes, those are white blood cells that specialize in the immune function, and
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then there are the lymphoid tissues. You have different types of lymphoid tissues—the
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central and peripheral. So these are both what we call SDLs, and these are self-directed
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learning. So you can imagine that as if this information were in your workbook and you
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were filling this in in your workbook. So for example when we look at the phagocytes, I’ve
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shown the phagocytes here for you. Neutrophils function as phagocytes. These are types of
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leukocytes. Monocytes are found in the blood, and when they move into the tissue we change
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their name, and now we call them a macrophage. And then the cell in the middle is called
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the dendritic cell. Look at it; it looks like it’s got dendrites on it, right? So these
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are all phagocytes. All of these will phagocytose foreign material. So I’ve left you a question
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here that says, “What are the four fixed macrophages and where are they found?” I’m
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going to give you one of them, the microglia, just to give you a starter on that question.
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Now the other cells that are very important in mounting the immune response are the lymphocytes.
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So again, these are also white blood cells, and there’s various types of lymphocytes
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that we’re going to discuss in detail later. But to get you started on lymphocytes, I’ve
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got a question here that says, “Most null cells”—so you need to figure out what
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a null cell is—“these are considered natural killer cells.”
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So we abbreviate natural killer cells NK and then cells. Those
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are very important in fighting certain kind of infections. Are they bacterial or are they
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viral? So I’ll let you finish filling out that fill in the blank there.
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Now the mast cells and dendritic cells are also self-directed learning. So the question
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there for you to answer is where are the mast cells found—what do they secrete? What is
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the function of a dendritic cell, and what are the four types? Okay, then you have other
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leukocytes that are important in secreting chemicals. For example: eosinophils. So when
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you think about eosinophils, these are white blood cells that are really important in allergic
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reactions, but they’re also very important in that they secrete chemicals that will dissolve
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or kill parasites. So from before when I mentioned that you could have a tapeworm that's eight, 10,
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12, 20 feet long, there’s no way for an eosinophil to engulf a worm of that size. And so rather
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than engulf it, eosinophils can actually secrete these chemicals that dissolve them. Then there
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are other leukocytes called basophils that release some chemicals as well. Basophils
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can release histamine, and histamine, if you remember, is it a vasodialator or vasoconstrictor?
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It’s a vasodialator, and basophils will also secrete heparin. Heparin is an anticoagulant
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or used as a blood thinner. So if you have a blood clot, they would put you on heparin
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treatment and what that would do is prevent further clotting, and it would also help break
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up that clot. Then we have the lymphoid tissues the central lymphoid tissues and the
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peripheral lymphoid tissues. So what I want you to do is to make a list. What are the
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central lymphoid tissues? And I’ll give you an idea here—you should be listing two
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of them. And then the peripheral lymphoid tissues—you should be listing six of these.
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And then what I want to know is what’s the connection between these central lymphoid
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tissues and the peripheral lymphoid tissues? So in other words, when you have lymphocytes
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in the central lymphoid tissue, do they always stay there or do they migrate out? Then you
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guys can complete these questions down below as well.