accompanies infection, but the presence of inflammation does not always mean infection has occurred. Many different types of cellular injury can cause inflammation. Invasion of body tissues by biologic agents results in inflammation. Exposure to physical agents results in inflammation. Allergic or autoimmune reactions result in an inflammatory reaction that may be localized or may result in systemic inflammation. Finally, neoplastic tumors may result in inflammation.
The Inflammatory Response Mechanisms
No matter what the cause, the physiologic mechanisms of inflammation are always the same. There are four parts to the process of inflammation; a response, a response, the formation of and . All four parts of the inflammatory response are interconnected and may overlap each other.
Vascular Response
Tissue damage causes immediate but transient . This occurs to diminish haemorrhage from any damaged blood vessels but is a temporary measure. Damage to tissue releases the chemical mediators such as histamine and kinins. These chemicals act to reverse the vasoconstriction and cause local vasodilatation and increased vessel . The combination of increased permeability and vasodilatation results in hyperemia of the damaged tissue and the accumulation of fluid in the extracellular space. We call this fluid . The migration of fluid from the blood vessel to the extracellular space leaves the blood more viscous, causing haemostasis. Haemostasis allows fibrinogen to be converted to fibrin promoting formation. A side effect of haemostasis is that some of the fibrin diffuses out of the vessels and collects in the extracellular space. The presence of fluid and fibrin, now called exudate, in the extracellular space is known as or swelling.
Cellular Response
The same chemicals that cause increased vessel permeability also cause leukocytes (WBC’s) to respond to injury. There are five steps to leukocyte response: margination, rolling, adhesion, diapedesis and chemotaxis. Chemotaxis: cells move in response to chemical stimulus Margination: accumulation and adhesion of WBCs to the endothelial cells of the blood vessel at the site of injury Rolling: circulating leukocytes bind to the inner wall of the vessel, causing the leukocytes to slow down and begin rolling along the inner surface of the vessel wall
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