Hello and welcome to Unit 6 of Biology 2402 Lab on Lymphatics and Immunity. Cue applause. There's none. But you'll hear my dog walking through in the background. Just ignore it.
It's fine. Okay, what does your lymphatic system do? It's part of your circulatory system.
You might think your circulatory system is your cardiovascular system, which is true. Your blood vessels, your heart, all circulate stuff. But that stuff leaks out.
into the fluids and it becomes what's called interstitial fluid. And as it filters through between your cells, it gets reabsorbed by these things called collecting vessels or lymphatic vessels, which are also part of your circulatory system because they're going to circulate that fluid back to your cardiovascular system. So the lymphatic system is kind of like a shadow, really weak, open circulatory system.
Alright, well now there's a lot of stuff that's been put up in the videos and photos that I'm not going to go into as much detail on here. But you'll have to know the difference between vessels, lymph nodes, the various different lymph organs, and the tissues are found in different spots. Some examples are Peyer's patches and tonsils and the appendix, which I'll talk about later in a little bit more detail.
The main filtering sites are your lymph nodes. You know, a few hundred of those in your body that have a lot of white blood cells. Your lacteals are in your intestine, and they do a specialist job of absorbing lipids. And after the lymph goes through this big filtering process, it's going to end up back by your collarbones here, and it's going to dump into your subclavian veins right in these two spots up there by your shoulders. And stop doing that.
And next. So here we go. Here's a list of some of the organs and structures.
So thymus, this is located just above your heart. You guys know where it is. It's mainly for T lymphocyte T cell maturation. So it's kind of an immune system structure. Your immune system and your lymphatic system really work together.
Your lymphatic system circulates the stuff and your immune system cleans it out. Your spleen, which is that big strap-like organ that's located just underneath your stomach, kind of on your left-hand side, has a couple of different identifiable structures inside of it. The white pulp and red pulp, and I'll show you that in the next slide. Tonsils at the back of your throat.
They have lots of B and T cells and macrophages, of course. Those guys are everywhere. Think about the tonsils. They're located right at the entrance to your digestive system.
So it's kind of at the entrance, the border between the outside world and your inside world. So you want to kind of screen what you're taking in. Your tonsils have lots of immune system cells that are located there specifically to kill bacteria, to prevent bacterial infections. If you've ever had tonsil stones, which are these little lumps that you'll get at the back of your throat. Sometimes they're little white or gray lumps, little wads of stuff.
They're gross. I remember the first time I ever had one was I was in grade school and I coughed by the side of a pool and I saw this little white thing. Well, that was a tonsil stone. And it's a bunch of dead white blood cells and dead bacteria that it's just basically a big pile of microorganism corpses.
I don't get them anymore. But they're cool if you do. Don't worry about it.
Your appendix, you might think of as vestigial. It's really not. It has a useful function.
I mean, if you get it removed, you're going to be okay. But it's mainly there to house all of this lymphoid tissue to prevent. bacteria that want to get into your small intestine from getting there from your large intestine.
And I'll mention that later. And also maintains its little pocket for beneficial gut flora, gut bacteria. Nodules can be located anywhere. Lymph nodes are actually nodules. But anytime you find a concentrated patch of lymphoid material, you're basically looking at a nodule.
And as I mentioned, lacteals are specialists. They're kind of They're interesting. They're kind of really a unique thing in your lymphatic system in that they are there to help your digestive system. They're going to absorb fats from your digestive system.
All right, let's go into some detail here in your spleen. You can see over here on the right, I've got a slide image of the spleen. These darker colored sort of purple areas are what they call white pulp.
They're called white pulp because when you look in there microscopically, you see loads and loads and loads of white blood cells, loads of lymphocytes. The rest of it, all this other area, all this stuff out here, everything that isn't one of these little purple spots is called red pulp. And that's basically a blood storage and filtering location. The white pulp are these little pockets of specialized lymphoid tissue with lots of B and T cells and also macrophages. Splenic cords are simply these sort of things right here, right?
See these little, they're actually continuous with the outside. There's probably one that would come in right here like this. So they're continuous with the capsule on the outside and they're kind of they provide a structural support for the inside of that organ for all the reticular fibers. Next slide I said.
Bugger what happened? That was the next slide. All right.
So here we go. Lymph nodes you've already I've already highlighted those in orange. So you have to know them got about 500 of them all throughout your body. They're all connected by vessels to each other.
Vessels can either be afferent, which means towards. So these are afferent like this or efferent like this. And you're going to have multiple afferent ones probably with usually one large efferent one.
What happens is as that lymph is being picked up from all over the body, it gets concentrated in these lymph nodes. And it filters through these what they call germinal centers. right here, these little locations.
And germinal centers are places where you've got loads of B cells that are proliferating. They're making copies of themselves. B cells, which you will learn in the lecture, are the cells that produce antibody.
And antibody targets antigens. We talked a little bit about this in the blood chapter. So the B cells make loads and loads of themselves. And the T cells also become activated, so you get a real amped up immune response. Those B cells and T cells target all of the pathogens that may be brought in through these afferent vessels.
As the lymph filters through the cortex, which is this outer blue area, in this case it's not blue, but it's the outer area, and you'll see these lymphatic, these... these follicles in the periphery. So that's one way you can tell a lymph node is that these circles are all scattered throughout the outside.
The spleen had them kind of scattered all throughout the inside. Anyway, as it filters through, you get down in here into the medulla, which still has lots of T and B cells. This is where they all end up concentrating.
So T and B cells that you make out here will get moved in here, and then they hang out in the reticular fibers. and just let the game come to them, right? They let all those bacteria come to them. There's lots of macrophages, so you've got a real killing ground for these pathogens. And then hopefully lastly, this program's responding a little slowly.
Let's see what happens. Apologize. There it goes. This is kind of a close-up view of your small intestine. On the right over there, we see a a model which you'll have in the photos of the mucosa which is here and this I'm sorry which is here and the submucosa which is here of the small intestine specifically the last stretch of it called the ileum these big blobs here are called Peyer's patches these finger like projections are called villi villus being singular and the green tube right down the middle is called the lacteal.
So the lacteal picks up fats. The whole villus picks up all of these digested nutrients, proteins, and carbohydrates, and so on. But the fats go into the lacteals and go into the lymphatic system and then go get pooled and recycled and eventually get to the liver where you break them down and do what you want with them.
Well, that was kind of brief, which you're probably thankful for. make sure you do look at those photos and watch my videos okay because in the in the photos i've labeled some things and and told you what they are and in the videos i describe it as i go if you have any questions feel free to stop by my office hours or email me thank you