In this video, we're going to talk briefly about the 3rd step of the inflammatory response, which is vasodilation. Vasodilation is the dilation or the enlargement of the blood vessels that increases the permeability of those blood vessels. The increased permeability allows for cells of the immune system to leave the bloodstream and enter the site of infection. This increased permeability is in response to inflammatory mediators. Inflammatory mediators that are released by mast cells lead to vasodilation, the enlargement of the blood vessels, and the increased permeability of those blood vessels.
The term diapedesis refers specifically to the migration of immune system cells through the intact walls of the blood vessels into the infected tissue. Additionally, the term exudate refers specifically to the fluid mix of blood plasma, proteins, and immune cells that exit the bloodstream to the infected site. Recall from some of our previous lesson videos that neutrophils are the first type of cells to be recruited to the site of infection. They are the first phagocytes that are recruited. Taking a look at our image down below, we have the 3rd step of the inflammatory response, which is vasodilation and diapedesis. You'll notice here that the cells of the infected area are infected with many microbes. Upon releasing those inflammatory mediators, mast cells lead to vasodilation. Here we have dilated blood vessels, labeled as dilated blood vessels. These dilated blood vessels increase the permeability of the blood vessels, allowing for diapedesis. Diapedesis, again, is the migration of immune cells from the blood into the site of infection. Macrophages and neutrophils can be recruited, and it's the neutrophils that are first recruited to the site of infection.
This concludes our brief lesson on the 3rd step of the inflammatory response, vasodilation. 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. I'll see you all in our next video.
