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