Tissue inflammation is the body’s response to damage that includes direct physical injury, infected cells, or other pathogens such as bacteria, allergens, viruses, and debris. Many different areas of the body can experience tissue inflammation including the skin, muscles, tendons, nervous system, immune system, and circulatory system. Depending on the trigger, tissue inflammation can either be an acute, immediate response or a chronic, long-term response. While beneficial in some cases such as wound healing and disease prevention, inflammation can also have negative consequences for the body.
Acute tissue inflammation generally occurs quickly in response to a sudden injury or infection. At the site of injury certain immune cells, such as mastocytes and dendritic cells, release inflammation mediators to induce changes in the body. These mediators cause vasodilation, or widening of the blood vessels to increase blood flow, fluid buildup, swelling, heat in the injured area, and pain, all of which serve to eliminate any potential pathogens or close up a newly formed wound. The increased pain is a signal to the body to keep the infected or injured area safe while the tissue inflammation process acts to eliminate the pathogens or heal the injury.
In addition to these system-level responses, cellular-level acute inflammatory responses also help to rid the body of potential pathogens. White blood cells, such as neutrophils and macrophages, congregate at the site of infection by a response known as chemotaxis, in which the cells follow chemical signals that lead them to the infection. Here, they will either emit anti-microbial proteins into the area to combat the pathogens or they will engulf the pathogens through phagocytosis, or absorption of the pathogen molecules. These white blood cells can engulf numerous bacteria, causing them to grow in size and collect in the site of infection. For the general acute tissue inflammation response to remain active, continual signaling must be received because once the pathogen is removed or the injury is mitigated, inflammation is no longer necessary and the process is halted.
Chronic tissue inflammation occurs over a long period of time, and it features the constant cyclical process of cellular death followed by healing in the inflamed area. Occasionally, this type of tissue inflammation can lead to inflammatory disorders, especially autoimmune disorders. Of these, major disorders include atherosclerosis, or chronic inflammation and hardening of the blood vessels, and pronounced allergies. Anaphylaxis, which is a form of hypersensitive allergic reaction, can cause the throat to inflame and close, making it a serious concern for those who have severe allergies. Similarly, atherosclerosis can lead to increased blood pressure and increased risk of heart attack.