21. The Immune System
Steps of the Inflammatory Response
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this video, we're going to talk briefly about the 3rd step of the inflammatory response, which is vasodilation. And so vasodilation is the dilation or the enlargement of the blood vessels that increases the permeability of those blood vessels. And the increased permeability allows for cells of the immune system to leave the bloodstream into the site of infection. And so this increased permeability is going to be in response to inflammatory mediators. And so inflammatory mediators that are released by mass cells will lead to vasodilation, the, enlargement of the blood vessels and the increased permeability of those blood vessels. Now the term diapedesis refers specifically to the migration of immune system cells through the intact walls of the blood vessels into the infected tissue. And the term exudate refers specifically to the fluid mix of blood plasma, proteins, and immune cells that exit the bloodstream to the infected site. Now recall from some of our previous lesson videos that neutrophils are the very first type of cells to be, recruited to the site of infection. And so they are the first phagocytes that are recruited. And so taking a look at our image down below, we have the 3rd step of the, inflammatory response, which is vasodilation and diapedesis. And so what you'll notice here is that the, cells, the infected area here is infected with many microbes. And the mast cells, upon releasing those inflammatory mediators, it leads to vasodilation. And so here we have dilated, you can label these as dilated blood vessels. And these dilated blood vessels are going to increase the permeability of the blood vessels, allowing for diapedesis. And diapedesis, again, is going to be the migration of blood of immune cells from the blood into the site of infection. And so macrophages and neutrophils can be recruited, and again, it's the neutrophils that are the first to be recruited to the site of infection. And so this here concludes our brief lesson on the 3rd step of the inflammatory response, vasodilation, and we'll be able to get some practice applying these concepts and talk about the 4th and final step of the inflammatory response as we move forward in our course. So I'll see I'll see you all in our next video.
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