>>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 reeks 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.