About Inflammation
Inflammation is a reactionary response to any damage caused to the cells or organized cellular structures known as tissues. It is a mode of defense of the body of higher living organisms. This mode of response helps the body to protect itself against any injury, infection, and invasion by foreign organisms. The inflammatory response can be in any tissue or organ such as eye inflammation, throat inflammation, inflammation of the lungs, etc. The purpose of inflammation is the localization of white blood cells at the site of injury for the elimination of invading pathogens after which the process of healing starts. There are changes in the blood flow such as an increase in blood vessel permeability with increased migration of fluids involving proteins and leukocytes from circulation to the injury site.
Causes and Signs of Inflammation
The pathogens i.e. the external factors that can cause inflammation include microorganisms such as bacteria or viruses, or chemicals such as acids, alkalis, and oxidizing agents, that induce immunological responses. Other internal factors that can cause inflammation are autoimmunity and cell death. As the bacteria and viruses enter the body and infect the cells they give rise to inflammation. The bacteria usually release chemical substances such as endotoxins which cause the body to respond with inflammation. Physical forms of injury such as burns due to fire or radiation, frostbites, can cause extensive damage to the body and cells initiating inflammation.
Once the inflammatory response is initiated there are four signs that represent the action. These four cardinal signs are redness, heat, tumor, and pain. They are named in Latin as follows: rubor for redness, calor for heat, tumor for swelling, and dolor for pain as described in the 1st century AD. All the four signs are explained below:
Redness: Dilation of small blood vessels in the area of injury.
Heat: Increase blood flow through the area and is experienced by the skin and other peripheral parts of the body.
Fever: Rise in tempurature of the body because of chemical mediators of inflammation.
Pain: Caused by the distortion of local tissues because of selling or edema which happens because of accumulation of fluid outside the blood vessels, or by inflammatory chemical mediators like serotonin, bradykinin, and prostaglandins.
As a consequence of all these events surrounding the four signs of inflammation, loss of function of the injured/inflamed tissue can occur. It inhibits mobility in the circulation because of pain or severe edema.
Examples of Inflammation
An example of inflammation is eye inflammation. Generally, eye inflammation is caused by viruses or bacteria. The most common form of eye inflammation are conjunctivitis or pink eye. It is an infection of the transparent membrane (conjunctiva) lining the eyelid covering the white part of the eyeball. The inflammatory signs, in this case, include redness, itchiness, and teardrops. Usually, it heals on its own but taking treatment such as antibiotics for bacterial conjunctivitis makes the healing faster.
Throat inflammation is another example of inflammatory organs. Pharyngitis and tonsillitis are the most common forms of infection-causing throat inflammation. Although most of such infections are caused by viruses, bacteria, fungi, parasites and cigarette smoking can induce infection resulting in throat inflammation. The symptoms of inflammation include redness, swelling, heating, and pain in the infected area. The sore throat can be treated by taking more fluids, but antibiotics can be used only when necessary.
Inflammatory acne is caused by bacteria, oil, or dead skin cells depositing in the pores of the skin. Propionibacterium acnes (P. acnes) is one of the specialized bacteria that causes acne. The signs of inflammatory acne include redness, and swelling by the clogging of the pores. There is another kind of acne is the non - inflammatory acne which is not caused by bacteria.
Types of Inflammation
The inflammatory response is of two types depending on the duration. The inflammation that stays for a few days is acute inflammation and the one that stays for a longer period of time is known as chronic inflammation. Both the kinds of inflammation are explained in detail below:
Acute Inflammation
Of the two types of inflammation, acute inflammation is the one that lasts for short periods. As soon as there is an injury, within an hour the white blood cells arrive at the site following a trail of chemicals released by the body cells that act as attractions. The white blood cells at the sites are the phagocytes that eat the damaged tissue and cell debris and ingest any foreign pathogens to call out more specialized white blood cells. When the injury persists mature monocytes start appearing at the local site of the injury which also usually starts appearing after 24 to 28 hours. Also, it can lead to another type of inflammation, chronic inflammation.
Following the period of acute inflammation, healing and repair and suppuration follow and are hugely dependent on the type of tissue and the amount of tissue damage depending on the cause of injury. The healing process as new cells takes place instead of the old ones. The damaged cells that are capable of proliferation, regenerate. But in the process of healing, it is important that the tissue structure is maintained especially after severe damage, otherwise, it can lead to another disease that can be fatal. One such example is liver cirrhosis. There is also pus formation in some cases, a phenomenon called suppuration. The pus formation happens because of the collection of damaged cell debris, dead and dying neutrophils, fluid leaks from blood vessels, etc. Certain bacteria of the genus Staphylococcus and Streptococcus also release fluid that adds to the pus formation. In the case of boils, the pus formation is easily removed by bursting but at other times it needs to be surgically removed. Once it is removed the regeneration of cells and tissue replaces the damaged site which also leaves a scar.
Chronic Inflammation
Prolonged inflammation is known as chronic inflammation. It may or may not be an extension of acute inflammation. Independently, chronic inflammation is caused by certain organisms like tuberculosis bacteria, fungi, protozoa, and metazoan parasites. This condition usually arises when the invading bacteria have become immune to the immune system of the body. Also, when the immune system of the body is sensitized to the cells and chemicals at the injury site, many times in case of autoimmunity diseases, chronic inflammation results. Chronic inflammation can be harmful and deadly. Proper treatment in consultation with the doctor can help control damage and maintain the health of the body.
FAQs on Inflammation
1. What is inflammation in biology?
Inflammation is the body's natural, protective response to injury, infection, or irritation. It is a fundamental part of the innate immune system, designed to eliminate the initial cause of cell injury, clear out dead cells and damaged tissues, and initiate tissue repair. It is not an infection itself, but a biological process to fight potential infection and heal.
2. What are the five cardinal signs of inflammation?
The five classical or cardinal signs of inflammation are crucial for its identification. These signs, first described by Celsus and later with the fifth added by Virchow, are:
- Redness (Rubor): Caused by increased blood flow to the affected area.
- Heat (Calor): Also due to increased blood flow and metabolic activity.
- Swelling (Tumor): Caused by the accumulation of fluid (exudate) in the tissue space.
- Pain (Dolor): Results from the release of chemicals that stimulate nerve endings, as well as pressure from swelling.
- Loss of Function (Functio laesa): The inflamed area may have reduced mobility or function due to pain and swelling.
3. What are the primary triggers or causes of inflammation?
Inflammation can be triggered by a wide range of factors that the body perceives as harmful. The main causes include:
- Pathogens: Infections caused by bacteria, viruses, fungi, or other microorganisms.
- Physical Injury: External injuries like cuts, fractures, burns, or frostbite.
- Chemical Irritants: Exposure to toxins, acids, or other harsh chemicals.
- Immunological Reactions: Hypersensitivity or autoimmune responses where the immune system mistakenly attacks healthy body tissues.
- Ischemia: Lack of blood supply to a tissue, which causes cell death and triggers inflammation.
4. What is the difference between acute and chronic inflammation?
The primary difference lies in the duration and outcome. Acute inflammation is a short-term response, typically lasting for a few days. It is characterised by the classic signs like redness and swelling and is essential for healing. In contrast, chronic inflammation is a prolonged, dysregulated response that can last for months or even years. It often involves different immune cells (like lymphocytes and macrophages) and can lead to tissue destruction and diseases such as arthritis or heart disease.
5. How do key immune cells like neutrophils and macrophages contribute to inflammation?
Neutrophils and macrophages are critical players in the inflammatory process. Neutrophils are usually the first responders. They are phagocytic cells that arrive quickly at the site of injury or infection to engulf and destroy pathogens. Macrophages arrive later and have a broader role; they also perform phagocytosis but are crucial for cleaning up cellular debris and dead neutrophils. Furthermore, macrophages release signalling molecules called cytokines that help coordinate the repair process and can either sustain or resolve the inflammation.
6. Why is the inflammatory response often called a 'double-edged sword'?
Inflammation is considered a 'double-edged sword' because it is both essential for survival and capable of causing significant harm. On one hand, the acute inflammatory response is protective—it localises threats, removes harmful stimuli, and initiates healing. Without it, infections would go unchecked and wounds would not heal. On the other hand, if the response is excessive or becomes chronic, it can lead to damage to healthy tissues and is implicated in the development of many diseases, including autoimmune disorders, neurodegenerative conditions, and cancer.
7. How does the body naturally resolve inflammation and start the healing process?
The resolution of inflammation is an active, highly regulated process, not just the stopping of the initial response. It involves several key steps: a switch in the type of chemical mediators produced, from pro-inflammatory (like prostaglandins) to anti-inflammatory (like lipoxins); the apoptosis (programmed cell death) of neutrophils; and the clearance of these dead cells and debris by macrophages. This 'clean-up' phase is critical as it signals the body to stop the inflammatory response and begin tissue regeneration and repair.
