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.