 Hey everybody, Dr. O here. In this video, we're going to talk about the inflammatory response, which is one of your non-specific defenses. Inflammatory response is going to help bring in immune cells to fight infections, clear debris, help wound healing, doesn't really matter what the source of the infection or injury is. That's why it's a non-specific defense. First let's talk about the four cardinal signs of inflammation, which is redness, swelling, heat, and pain. So you just have to know them in Latin, rubor, caloric, et cetera, but don't worry about that. Redness, swelling, heat, and pain. Some would call the fifth cardinal sign of inflammation a loss of function, and that comes with the pain and swelling in the area. So redness, swelling, and heat are all going to be caused by the same thing, an increase in blood flow, because remember blood is warmer in the rest of your body and then blood is going to bring all this fluid with it. So that's going to be the redness, the swelling, and the heat. Pain is going to be caused by the tissue damage and the chemicals that are released during the inflammatory process. So you see here the key immune cell when it comes to inflammation is the mast cell. So we have talked about them. Mast cells are very similar to basophils. They used to be believed to be the same cell. The key difference is basophils stay in your bloodstream and release histamine, heparin, et cetera. Mast cells are going to be found out in your tissues and they'll do the same thing. So the key chemical here is going to be histamine as you see it being released in the top of the image. Histamine is going to be a basodilator. It's going to increase the movement of fluid into the area. It's also going to make your capillaries more leaky. So you're going to force out more fluid to become interstitial fluid. So not only is there an increase in blood flow to the area, but you're going to have more edema, more interstitial fluid is going to be collecting as well. Other cells are involved, not just the mast cells. Neutrophils can come in, especially if there's bad bacterial infections. They will come in and engulf the bacteria. They'll eat so many of them they die. So neutrophils and all the contents of these dead cells is actually what causes the pus that would be at the side of an infection. Other cells are going to be important. Other chemicals are going to be important too. The other key chemicals would be the leukotrienes. They're important because they're the ones that call in the neutrophils and say, hey, there's bacteria here that have to be dealt with. But to me, the key one besides histamine and then heparin, which is a blood thinner, is going to be the prostaglandins. So prostaglandins are going to be cells that cause vasodilation. They relax smooth muscle and it's also going to cause pain. I mentioned this in another video, but this is why your anti-inflammatory drugs like ibuprofen work. They block prostaglandins, which is going to block some of the pain and some of the swelling associated with the inflammatory response. So why do we have an inflammatory response? You call in this blood, you call in these blood cells to deal with the infection if there is one, to clear debris so we can heal the wound, right? Inflammatory response is a good thing. So acute inflammation at the site of tissue damage caused by mechanical trauma or infection, that's great. But chronic inflammation is what appears to lead to a lot of other health problems. That's a talk for a separate video here. All right. Here we just see an example. So here we see an ear drum in the middle ear that looks normal versus an inflamed one. So just to show you that. And then here we do see the mast cells. So mast cells can certainly be in your bloodstream. That's how they get around the body, but what makes them different than your basophils, which we covered with the other white blood cells, is they will go into your body's tissues. Okay. So that is the inflammatory response, one of your non-specific defenses. I hope this helps. Have a wonderful day. Be blessed.