Introduction to Inflammation: Study with Video Lessons, Practice Problems & Examples

Inflammation is a coordinated immune response to infection or tissue damage, characterized by five cardinal signs: swelling, heat, altered function, redness, and pain, remembered by the acronym SHARP. There are two types of inflammatory responses: acute inflammation, a short-term response marked by neutrophils, and chronic inflammation, a long-term response involving macrophages and T lymphocytes, which can lead to granuloma formation. Understanding these processes is crucial for recognizing how the body defends itself against pathogens and manages tissue repair.

Introduction to Inflammation

This video, we're going to begin our introduction to inflammation. And so first, we need to recall from some of our previous lesson videos that we already briefly defined inflammation as a coordinated set of events that occurs when the body detects an infection or tissue damage. Now, there are 5 cardinal signs of inflammation that you can remember by using this acronym SHARP. And so the 5 cardinal signs of inflammation are swelling, heat, altered function, redness, and pain. And so if you can remember SHARP, then you'll be able to remember the 5 cardinal signs of inflammation: Swelling, heat, altered function, redness, and pain. And so over here, we have a little cartoon just to help you remember this SHARP acronym. And so notice here we have Doctor Clutch Prep over here, and he says, "Wow, this sword is so sharp." And notice he had a little accident here, and Doctor Clutch is now feeling the 5 cardinal signs of inflammation just by remembering this SHARP acronym right here. And so, as we move forward in our course, we'll be able to talk a lot more about the steps of inflammation and different types of inflammation as well. But for now, this here concludes our brief introduction to inflammation, and I'll see you all in our next lesson video to learn more.

Types of Inflammatory Responses

In this video, we're going to briefly introduce 2 types of inflammatory responses. And so once again, there are 2 types of inflammatory responses, and they are acute inflammation and chronic inflammation. Now, acute inflammation is characterized by being a short-term immune response. The symptoms are going to develop very rapidly, and they're going to last only a short period of time, for example, just a few days. Examples of acute inflammation include inflammation that's due to the common cold, flu, headache, and joint pain, all associated with inflammation that only lasts a short period of time, just a few days.

Now, chronic inflammation, on the other hand, is characterized by a long-term immune response. The symptoms of chronic inflammation develop very slowly rather than developing rapidly, and they last a long period of time, for example, many years or perhaps even the entire lifespan of the organism. Examples of chronic inflammation include inflammation due to heart disease, cancer, Crohn's disease, or arthritis.

If we take a look at our image down below, notice on the left-hand side we're showing you a table that's comparing acute and chronic inflammation. And so notice on the y-axis we have the severity of the inflammation, and on the x-axis what we have is time. And what you'll notice is the red curve that you see here corresponds with acute inflammation because notice that it is lasting just a short period of time, with the x-axis just being a few days. And notice that the purple curve that you see here corresponds with chronic inflammation. And once again, chronic inflammation is characterized by being a long-term inflammation that can last years, perhaps even the entire lifespan of the organism.

Now on the right over here, we're showing you our map of the lesson on Innate Immunity. In this video, we're specifically focusing on the second line of defense and the innate effectors, specifically inflammation. Here in this video, we're distinguishing between acute inflammation and chronic inflammation. As we move forward in our course, we're going to talk even more about acute inflammation and even more about chronic inflammation. But for now, this here concludes our brief introduction to these two types of inflammatory responses, acute inflammation and chronic inflammation, and we'll be able to learn more about them as we move forward so I'll see you all in our next video.

Acute Inflammation

This video, we're going to talk a little bit more about acute inflammation. Recall from our previous lesson video that acute inflammation is characterized by a short-term immune response where symptoms develop very quickly and last only a short period of time, such as just a few days. Acute inflammation is marked by an abundance of neutrophils. These neutrophils gather in the infected and damaged area. The main goal of acute inflammation is to quickly recruit immune cells to the site of damage or infection. Neutrophils are the first to be recruited to the area. These cells are the first to arrive at the site of infection.

If we take a look at our image below, on the left-hand side here, we're focusing on our map of the lesson showing the innate effector actions, and we've already discussed phagocytosis. So here in this video, we're focusing on acute inflammation. Here we have a little cartoon that's focusing on acute inflammation. Notice that we have a person here who is outdoors, and a bug, such as a mosquito, lands on this person. Then, notice that this person is saying, "Ow, a bug bit me," as the mosquito bites them. Notice that acute inflammation results from the bug bite. Just a few days later, notice that the inflammation has subsided. Again, acute inflammation only lasts a short period of time, just a few days.

This concludes our brief lesson on acute inflammation, how it is characterized by an abundance of neutrophils, and how we'll be able to apply these concepts as we move forward. Then, we'll talk a little about chronic inflammation. I'll see you all in our next video.

Which of the following answers is an inflammatory mediator that stimulates vasodilation allowing immune cells to enter the site of infection?

• A. Collagen.
• B. Serotonin.
• C. C3b protein.
• D. Histamine.

Which of the following scenarios would not result in an episode of acute inflammation?

• A. An individual having rheumatoid arthritis, an inflammatory disease that degrades the joints over a lifetime.
• B. An individual having a painful sensation around a vaccine injection site for a few days after vaccination.
• C. An individual having a swollen ankle for a week after falling down a set of stairs.
• D. An individual having a painful, red wound for a few days after being scratched by a cat.

Chronic Inflammation

In this video, we're going to talk some more details about chronic inflammation. And so first we need to recall from some of our previous lesson videos that we already defined chronic inflammation as a long-term immune response, where symptoms are going to develop slowly, and they are going to last a long period of time. For example, several years. Now, unlike acute inflammation, which is characterized by an abundance of neutrophils, chronic inflammation is characterized by an abundance of macrophages, giant cells, and T lymphocytes or T cells. Now recall that giant cells are the fusion of 2 macrophages, and T lymphocytes or T cells are cells that are part of adaptive immunity. These macrophages, giant cells, and T lymphocytes can accumulate to form what is known as a granuloma. And so granulomas are really just concentrated groups of cells that are important for retaining or walling off microbes that cannot be easily destroyed.

If we take a look at our image down below, notice on the left-hand side we're showing you our map of the lesson on these innate effector actions, and we're specifically focusing on inflammation and chronic inflammation here. Once again, chronic inflammation is characterized by a long-term immune response. Notice in this cartoon on the left over here, we have a person whose knee is displaying some inflammation through rheumatoid arthritis. Notice that several years later, a long period of time later, this arthritis and inflammation are still occurring. This is an example of chronic inflammation, long-term inflammation that can last a long period of time.

Now down below what we're showing you is, once again, chronic inflammation and the granulomas that can form during chronic inflammation. Over here what we have is the Mycobacterium tuberculosis, which is bacteria that causes tuberculosis. Then, we have the image of the macrophage, B cells, and T cells. What you'll notice is that these granulomas are going to consist of a bunch of immune system cells that are gathering to create a structure to wall off and block and retain the bacteria so that the bacteria are not capable of spreading. This really only occurs during severe chronic long-term inflammation. Here's an image of the granuloma in the lymph node.

This here concludes our brief lesson on chronic inflammation, as well as granulomas. 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.

A scientist is analyzing the cells from a granuloma tissue sample. Which type of immune cell is the scientist least likely to find in this sample?

• A. T cells.
• B. Macrophages.
• C. Neutrophils.
• D. Giant cells.

The disease tuberculosis (TB) is a serious bacterial infection characterized by granulomas typically found in the lungs. What characteristics would a TB granuloma have?

• A. A large mass of immune cells surrounding the Mycobacterium tuberculosis thus stopping the spread of bacteria.
• B. A region of scar tissue created by Mycobacterium tuberculosis.
• C. A region of tissue growth to heal the damage caused by Mycobacterium tuberculosis.

Here’s what students ask on this topic:

What are the five cardinal signs of inflammation?

The five cardinal signs of inflammation are swelling, heat, altered function, redness, and pain. These can be remembered using the acronym SHARP. Swelling occurs due to the accumulation of fluid in the tissues. Heat is a result of increased blood flow to the affected area. Altered function refers to the impaired function of the inflamed tissue. Redness is caused by the dilation of small blood vessels in the area. Pain results from the release of chemicals that stimulate nerve endings. Together, these signs indicate the body's response to infection or tissue damage.

What is the difference between acute and chronic inflammation?

Acute inflammation is a short-term immune response that develops rapidly and lasts for a few days. It is characterized by an abundance of neutrophils at the site of infection or damage. Examples include inflammation from a common cold or a bug bite. Chronic inflammation, on the other hand, is a long-term immune response that develops slowly and can last for years or even a lifetime. It involves macrophages, giant cells, and T lymphocytes, and can lead to the formation of granulomas. Examples include inflammation from heart disease or rheumatoid arthritis.

What role do neutrophils play in acute inflammation?

Neutrophils are the first immune cells to arrive at the site of infection or tissue damage during acute inflammation. Their primary role is to quickly respond to and neutralize pathogens. They achieve this by engulfing and digesting microbes through a process called phagocytosis. Neutrophils also release enzymes and antimicrobial proteins that help to kill pathogens. Their rapid response is crucial for controlling infections and initiating the healing process in the affected tissues.

What are granulomas and how do they form during chronic inflammation?

Granulomas are concentrated groups of immune cells that form during chronic inflammation to wall off and contain pathogens that cannot be easily destroyed. They consist mainly of macrophages, giant cells (fused macrophages), and T lymphocytes. Granulomas form when the immune system attempts to isolate and prevent the spread of persistent pathogens, such as Mycobacterium tuberculosis, the bacteria that cause tuberculosis. These structures help to contain the infection but can also contribute to tissue damage and impaired function over time.

How does chronic inflammation contribute to diseases like heart disease and cancer?

Chronic inflammation contributes to diseases like heart disease and cancer by causing prolonged tissue damage and creating an environment that supports disease progression. In heart disease, chronic inflammation can lead to the buildup of plaques in the arteries, increasing the risk of heart attacks. In cancer, chronic inflammation can promote genetic mutations and create a microenvironment that supports tumor growth and metastasis. The persistent presence of inflammatory cells and cytokines can disrupt normal cellular functions and contribute to the development and progression of these diseases.