Inflammatory process: When the body is invaded by germs or a bacterial infection, the body’s immune system will respond to it by creating antibodies and sending white blood cells to fight the germs or infection. As the immune system interacts with the invading pathogen, the infection site will go through the inflammatory process. This process will vary, depending on area that is being affected. It usually will consist of an injury response, an immune response, tissue healing and wound repair. As the body goes through bacterial or physical trauma, it will immediately respond by sending white blood cells to the area. Produced in the lymph nodes and in bone marrow, white blood cells are released into the bloodstream, devouring and cannibalizing the invading pathogens. As part of the inflammatory process, the localized area usually will become tender and particularly sore. If the trauma is on the skin, then the area also will be prone to discoloration. The inflammatory process is closely linked to the immune system. The immune system will dilate the blood vessels, forcing blood that is rich with oxygen and white blood cells to surround the trauma area. Inflammation is the accumulation of white blood cells as they surround and kill the invading pathogen. As the trauma area heals, there will be a certain amount of pus. The pus is a collection of dead cells from the invading pathogen as well as cells produced by the immune system. Some swelling usually will occur during the inflammatory process. Protein and water will surround the area, making the area inflamed and slightly disfigured. The protein will contain antibodies to protect the area from being re-infected and will encourage tissue growth and healing. Pain can be an ongoing component of the inflammatory process. As the physiological aspects of the trauma area change, the area can be continuously painful and tender. The inflammatory process usually ends as soon as the invading pathogen is eradicated or as soon as the trauma area heals. Pus formations will usually stop, the area will become stable, and inflammation will subside.
Role of neutrophils & monocytes:
Tissue Macrophage Is a First Line of Defense Against Infection. Within minutes after inflammation begins, the macrophages already present in the tissues, whether histiocytes in the subcutaneous tissues, alveolar macrophages in the lungs, microglia in the brain, or others, immediately begin their phagocytic actions.
When activated by the products of infection and inflammation, the first effect is rapid enlargement of each of these cells. Next, many of the previously sessile macrophages break loose from their attachments and become mobile, forming the first line of defense against infection during the first hour or so. The numbers of these early mobilized macrophages often are not great, but they are lifesaving.
Neutrophil Invasion of the Inflamed Area Is a Second Line of Defense. Within the first hour or so after inflammation begins, large numbers of neutrophils begin to invade the inflamed area from the blood. This is caused by products from the inflamed tissues that initiate the following reactions: (1) They alter the inside surface of the capillary endothelium, causing neutrophils to stick to the capillary walls in the inflamed area. This effect is called margination. (2) They cause the intercellular attachments between the endothelial cells of the capillaries and small venules to loosen, allowing openings large enough for neutrophils to pass by diapedesis directly from the blood into the tissue spaces. (3) Other products of inflammation then cause chemotaxis of the neutrophils toward the injured tissues, as explained earlier. Thus, within several hours after tissue damage begins, the area becomes well supplied with neutrophils. Because the blood neutrophils are already mature cells, they are ready to immediately begin their scavenger functions for killing bacteria and removing foreign matter.
