Steps of the Inflammatory Response - Video Tutorials & Practice Problems

Step 1: Tissue Damage & Infection

In this video, we're going to begin our lesson on the steps of the inflammatory response. And so really a series of just four events or four steps occur in the inflammatory response during tissue damage and infection of a micro. And so in this video, we're only going to focus on the very first event or the very first step of the inflammatory response, which is tissue damage and infection. But later in other videos, we'll talk about the other steps of the inflammatory response. And so in the first step of the inflammatory response, we have tissue damage and infection and so damage to the tissues allows microbes to bypass the first line of defense of innate immunity. So it can bypass our skin mucus membranes, ant microbes and things of that nature. And when they bypass the first line of defense, they can enter into the surrounding tissue cells. And immediately after injury, blood vessels will briefly constrict via vasoconstriction. Vasoconstriction is the constriction or the the narrowing of the blood vessels. And it does this in order to prevent blood loss. And so if we take a look at our image down below what we're showing you is the very first event of uh the inflammatory response which is tissue damage and infection by the microbe. And so notice in this image, it is an image showing you our skin. And so you can see the epidermis layer is at the top here and the dermis layer is right here and down below. Notice that the blood vessel is at the bottom. And what you'll notice is that uh when there is damage, like for example, when a sharp object penetrates into your tissues, uh what you'll notice is that some of our immune system cells are already going to be present in the tissues. For example, mass cells can be present in the tissues. But uh when there is a penetration by a sharp object like this, it creates the opportunity for microbes to infect the tissues. And so this tissue damage uh can lead to infection of a microbe. And once again, the blood vessels are going to briefly constrict to prevent a large amount of blood loss. And so this year concludes our uh lesson on the first event of the inflammatory response. And we'll get to talk about the other events of the inflammatory response as we move forward. So I'll see you all in our next video.

Step 2: Release of Inflammatory Mediators & Other Cytokines

In this video, we're going to talk briefly about the second step in the inflammatory response, which is the release of the inflammatory mediators and other cytokines. And so, in response to a microbe invasion or tissue damage, local mast cells uh which recall are very similar to basophils, but they reside in the tissues are going to release cytokines and inflammatory mediators. And so these mast cells are already residing within the tissues. As you can see here in this image and they will begin to release cytokines and inflammatory mediators upon an infection. And so inflammatory mediators really refers to messenger molecules uh messenger molecules that are specifically involved in the inflammatory response. For example, histamine is an example of an inflammatory mediator. And so the release of histamine will promote inflammation. Now, uh the release of inflammatory mediators will help to regulate changes in local blood vessels, potentially causing the local blood vessels to dilate as we'll talk about in the next step. And it will also signal immune system cells from the blood to the infected site, attracting immune system cells to the area of infection. And so if we take a look at this image down below, we're focusing in on the second step of the inflammatory response, inflammatory mediators and cytokines being released. And so, once again, these mass cells that are present in the tissues and reside in the tissues will begin to release cytokines and inflammatory mediators. And these cytokines and inflammatory mediators will cause changes to the local blood vessels and also signal immune system cells to uh travel uh from the blood c uh from the blood vessels to the area of infection to help uh eliminate the microbes. And so this year concludes our brief lesson on the second step of the inflammatory response. And we'll be able to talk about the third and the fourth steps of the inflammatory response as we continue to move forward. So I'll see you in our next lesson video.

In the inflammatory response, which immune cells are the first to begin the immune response to an injury?

• A. The neutrophil cells are the first to respond to the injury and begin removing invading microbes.
• B. The mast cells release inflammatory mediators to recruit other immune cells to the injury site.
• C. The macrophages release histamine to dilate the blood vessels allowing immune cells to enter the injury site.

Step 3: Vasodilation

In this video, we're going to talk briefly about the third 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 uh 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 uh 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 third step of the uh inflammatory response, which is vasodilation and diapedesis. And so, what you'll notice here is that the uh cells, the um infected area here is infected with many microbes and uh the mass cells upon releasing those uh inflammatory mediators, it leads to vasodilation. And so here we have dilated, we 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 year concludes our brief lesson on the third step of the inflammatory response vasodilation. And we'll be able to get some practice applying these concepts and talk about the fourth and final step of the inflammatory response as we move forward in our course. So I'll see you, I'll see you all in our next video.

Which of the following is needed for vasodilation and diapedesis to occur at an infection site?

• A. Mast cells releasing histamines and cytokines to dilate the blood vessels & recruit immune cells.
• B. Adhesion proteins on the endothelial cells of the blood vessels allowing the immune cells to leave the blood stream.
• C. Exudate full of blood, plasma, proteins and immune cells exiting the blood stream to the infection site.
• D. All are needed for vasodilation and diapedesis to occur at the site of an infection.

Step 4: Removal of Invading Microbes

In this video, we're going to talk about the fourth and final step of the inflammatory response, which is removal of the invading microbes. And so the fag acidic cells that migrated from the blood into the infected area are going to destroy or eliminate those invading microbes. Now, the neutrophils are going to remove microbes through degranulation or through phagocytosis. And macrophages are going to uh perform phagocytosis and engulf uh the cells uh the dead cells in the area to help destroy and eliminate all of the microbes that have invaded. And so, taking a look at this image down below the fourth and final step of the inflammatory response is phagocytosis of the invading microbes and removal of those invading microbes. And so notice in this image, we have neutrophile and we also have macrophages and uh together they will work to eliminate these microbes and remove those microbes. And so this here concludes our uh lesson on this fourth and final step of the inflammatory response. And so moving forward, we'll be able to get practice on these concepts and uh also continue to talk more about the innate uh immune responses. So I'll see you all in our next video.

Which immune cells are responsible for removing dead or damaged host material at an injury site?

• A. Macrophages.
• B. Mast cells.
• C. Neutrophils.
• D. Platelets.

The attraction of leukocytes to the area on inflammation is referred to as

• A. Parasitism.
• B. Infection.
• C. Phototaxis.
• D. Chemotaxis.

Damaging Effects of the Inflammatory Response

In this video, we're going to talk a little bit about the damaging effects of the inflammatory response. And so, although inflammation is designed to eliminate microbes and protect us from microbes, sometimes inflammation can result in significant damage to the host. And this is really accidental damage because again, the inflammatory response is supposed to be eliminating microbes. And so the inflammatory response can be somewhat similar to a sprinkler system in a building where the sprinkler system is designed to project water and eliminate and prevent fires. However, sometimes the sprinkler system can also cause accidental damage to electrical equipment. And so that's why the inflammatory response can be an analogy to a sprinkler system because it's designed to eliminate microbes, but sometimes it can cause accidental damage to the host. Now, depending on the location of where inflammation occurs within the host. Inflammation can actually be life-threatening. For example, if inflammation occurs in the brain, it can be very life-threatening. Now, the suffix itis is found in many disease names and it specifically means inflammation. And so you can find that suffix itis in the uh the term meningitis or encephalitis. And again, that suffix itis means inflammation. And so down below, we're showing you just an image of rheumatoid arthritis, which is basically inflammation that occurs in the joints. And uh meningitis and encephalitis are uh basically just inflammation of the meninges or the membranes of the brain or uh inflammation of the brain itself, which again can be life threatening. And so that's important to keep in mind about the inflammatory response that occasionally it can have some damaging effects. And so this here concludes our brief lesson on the damaging effects of the inflammatory response. And once again, we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which of the following statements about the inflammatory response is false?

• A. It includes vasodilation of the blood vessels and the release of immune cells from the blood stream.
• B. Neutrophils are the first cells to exit the blood stream during the inflammatory response.
• C. Apoptosis of infected cells triggers the inflammatory response.
• D. Chronic triggering of the inflammatory response can damage the host.
• E. Major signs of inflammation include: redness, swelling, heat, pain, and loss of function

Rheumatoid arthritis is an autoimmune disease, meaning that the body’s immune system attacks the body’s joint tissues. Why are many autoimmune diseases associated with chronic inflammation?

• A. The tissues the immune system is “fighting” are always present, so the inflammatory response does not shut off.
• B. The invading microbes are not easily killed and keep reforming causing chronic inflammation.
• C. The invading virus goes dormant in the body and later reemerges causing prolonged periods of inflammation.

Which of the following is FALSE in regards to inflammation?

• A. It is a component of the second line of defense.
• B. It is caused by antibody­-antigen complexes.
• C. It is a component of the first line of defense.
• D. It can be caused by endotoxins.