 Hey everybody, Dr. O. This video is going to be the introduction to a series of shorter videos on the non-specific defenses. So you have a non-specific half of your immune system, often called your innate immune system, and then you have the specific half of your immune system, often called your adaptive immune system. So the key difference is the specificity. Your non-specific defenses don't care what's there, right? They're either doing their job, like we'll see here in this video just being a barrier, and by doing their job, they're also inhibiting or killing microbes, or they're immune cells like your phagocytic cells that don't know what you are, they just know you don't belong and they will attack and destroy you or neutralize you in that fashion. And then we'll cover the cells involved in your specific immunity later. So let's start with just the barriers. What are the many things that are designed, at least as part of their job, to inhibit or control microbial growth just by their presence? So you see a list here, and I'll talk about some more than others, but you see the skin just being a barrier, I'll show you that in a separate video. We'll talk about sweat and sebaceous glands, the sebum that they produce. Salivary glands, great example because they produce lysozyme, which is really good at destroying the cell walls of gram-positive bacteria, so your saliva has an immune component to it. The stomach acid is a great one. The stomach pH can get as low as one even, or maybe even lower, to the low pH of the stomach. One of the reasons we have such an acidic stomach is to stop the movement of microbes that you're swallowed to keep them from going any farther from the stomachs. Now there are some microbes that can live in the stomach. There are microbes that can survive in all these environments, but their job is to greatly diminish the number of microbes that can cause a problem. We'll look at the mucosal surfaces and mucus production and how we get rid of mucus as well here. And the last one I want to focus on right here before we move to the next image is what's called your microbiome. The normal, healthy, good microbes that are part of your body. So they are a huge part of your immune system, mainly because of what's called competitive exclusion. They take up space, as long as you're covered inside and out with good microbes that are taking up space and using resources. There's not as much room for bad microbes. So a good example of this would be a C. diff infection. Those who work in healthcare know what C. diff is. You probably know what it smells like. It's disgusting, but almost all cases of C. diff happen after you take antibiotics. So the antibiotics wipe out a bunch of the good microbes, your normal flora or your microbiome, and that means there's now more room and more resources available for C. diff. The same can be said with yeast infections that occur after you take antibiotics. So your normal microbiome is there and it helps in other ways too. These good microbes also produce what are called antimicrobial peptides. Maybe they change the pH because pathogenic bacteria generally don't like lower pHs like some other microbes do. That's why you have a vaginal microbiome full of lactic acid producing organisms to keep the pH down so that the vaginal pathogens don't like to exist there as much. And this is so important. Having a healthy microbiome is so important that we're now seeing fecal transplants actually being used as a treatment for C. diff and among other conditions. So if someone gets a C. diff infection in their gut, which kills tens of thousands of Americans a year, one of the best treatments, probably the best treatment is to give them to transplant somebody else's fecal microbiome into them to help to help get rid of the C. diff or at least to hold it at bay. So that's just one really cool example of these nonspecific defenses. Let's walk through a few more here, some of these more barrier defenses. Here we see the skin. So first of all, your skin is covered in sebum and sweat and fats that make it a salty, dry, acidic environment that most microbes aren't going to like. And then also you're constantly sloughing off dead skin cells. So every time you slough off a skin cell, you slough off any of the microbes that were attached to it. So as long as you have this healthy skin barrier, that's going to keep a lot of infections at bay. The only problem is when we break the barrier, a pimple, a cut, a scratch, a bite, these can all lead to serious infections, surgery, leading to staff infections, those types of things. So the skin, when it's intact, works as a really good barrier. When it's not intact, it can be a source of infection. Here we just have mainly just fluids. So you see like your eye is protected by eyelashes. You've got a layer of fluid on your eyes. Tears are produced and then drained away. So that's called a flushing action. You see that as well with the urinary system. Your kidneys, ureters, and bladder usually produce sterile urine because it's constantly being flushed out. So just a flushing action can help control microbial growth. Then your eye is also protected by those eyelashes there. What else? Same thing. The ureter there in both males and females is going to constantly be flushed out with urine production. So those are some other examples of just what are called barrier defenses. Here we see ciliated cells. So you have ciliated cells. When I think of them, I generally think of your respiratory tract. So you're all of the openings into and out of your body. So your respiratory tract, gastrointestinal tract, they're all going to be lined with mucus and mucus is going to kind of capture and hopefully inhibit the growth and slow the growth of microbes. But you also have these ciliated cells that can carry away these microbes. So if microbes are trapped in the mucus in your airways, what's called the mucociliary escalator or just the ciliary escalator is going to carry this mucus full of trapped pathogens up to the back of your throat. I like to call it lung butter, where you can expel it, either coughing it out, swallowing it, those types of things. So ciliary action along with mucus would be other barrier defenses. Here we see just the goblet cells that actually produce mucus. So in this example, it would be producing mucus that lines your GI tract. So the mucus in your GI tract would capture some of these pathogens potentially and then be carried away in fecal material. So we have constant movement or this flushing action also occurs in your GI tract. All right. Then we just have some other chemical defenses. I've mentioned some of these already like lysozine, especially effective of breaking down gram positive bacteria. We talked about sebum controlling the growth of microbes in your skin. We've talked about a few of these, the stomach acid as well. What are some other important ones here? We'll cover complement proteins in a separate video. Last one then we'll talk about here would just be the lactoferrin. So lactoferrin is a compound found in saliva and tears and all over the place along with lysozine that traps and captures iron. So specifically microbes, pathogens love iron. So if you can capture iron and keep it away from these microbes, hopefully you can inhibit their growth. All right. So I don't care if you know any of these specifically, I just wanted to give you a wide variety of different nonspecific defenses, what are called barrier defenses. Most of these don't even know what they're doing, right? Just by existing, just by being there, they're inhibiting the growth of microbes. That's why you want intact skin. You want a low pH in your stomach. You want your body to be producing all of the mucus, et cetera, et cetera. Okay. So those are your barrier defenses, the first group of nonspecific defenses. I hope this helps. Have a wonderful day. Be blessed.