Inflammation is a beneficial local tissue response to the various of stimulus in the living body which have vasculature, and the central link of inflammation is vascular response. Any factors causing tissue injury may result in inflammation.
The general pathological changes of inflammation include alteration, exudation and proliferation in local tissue. The major changes of acute inflammation or early phrase of inflammation display alteration and exudation, and later phrase of inflammation or chronic inflammation show proliferation. The alteration is the process of injury, however the exudation and proliferation are the anti-injury one. The important sign of acute inflammation is the exudative pathological changes what reflects the vascular response, especially the exudation of inflammatory cells is the characteristic changes of acute inflammation. The compositions of exudate have defensive role in the local. The characteristics of acute inflammation are vascular and exudative changes, which include three interrelated process: ①the dynamic changes of bloodstream (inflammatory hyperemia).②the increased vascular permeability (inflammatory exudation).③the exudation of leukocytes (inflammatory infiltration). The leukocytes facilitated by the chemotactic agents reach the inflammatory sites through margination, pavement, adhesion and emigration from blood vessel, then recognize, phagocytose and kill pathogens. During the early phrase of acute inflammation, the main inflammatory cells are neutrophils, and the major cells are macrophages, lymphocytes and plasmocytes during the later phrase or chronic inflammation.
The inflammatory mediators from cells and body fluid mediate many steps of inflammatory response. Local vascular response, exudation of inflammatory cells, tissue injury and repair.
Inflammation and the various symptoms of inflammation such as redness, swelling, heat, pain, loss of function, fever and increased leukocytosis make the inflammation as a differented disease from the others.The aboving clinical pathologic appearances have a close relationship with the inflammatory mediators. Grasp the principles of inflammatory mediators has both theoretic and practical importance during the resolution of inflammation. However, there are many inflammatory mediators summarized as following: ① histamine, bradykinin, prostaglandin( PGI2, PGE2, PGD2, PGF2 α ) and nitric oxide( NO)may result in dilatation of the blood vessels. ② histamine, bradykinin, prostaglandin, leukotriene C4, D4, E4, PAF and substance P all increase permeability of vascular. ③ LTB4, C5a, production of the bacteria, cationic protein and chemokine are the factors which cause the exudation and chemotaxis of inflammatory cells. ④ prostaglandins have critical role in vascular dilatation, pain and fever. ⑤ IL-1 and TNF regulate the interaction between leukocytes and endothelial cells during early phrase of inflammation. ⑥ oxygen free radicals, lysosomal enzymes and NO result in tissue damage.
Systemic inflammatory response syndrome (SIRS) is a kind of sustained, excessive systemic inflammatory response which is secondary to severe trauma, infection, tissue necrosis and ischemia, and can be classified into three stages: the local inflammatory response stage, the limited systemic inflammatory response stage and uncontrolled systemic inflammatory response stage. A large amount of inflammatory cytokines into circulation stimulate the inflammatory mediators releasing and their endogenous antagonists can not inhibite them, then result in increased inflammatory mediators in circulation and damage of intact of endothelium of capillaries, dysfunction of systemic +organs.
The inflammation may be classified into exudative, alterative and proliferative inflammation according to its pathological changes. The exudative or alterative inflammation are almost acute inflammation, the former can also be classified into serous inflammation, fibrinous inflammation, purulent inflammation (phlegmonous inflammation, abscess, superficial suppuration and empyema) and hemorrhagic inflammation, The proliferative inflammation are almost chronic inflammation, of which granulomatous inflammation resulted from tuberculosis, leprosy, Crohn disease, fungi infection and foreign body response has special characteristics, such as formation of monocytes/macrophages and their derived cells granuloma. Sometimes, the disease may be diagnosed according to the characteristics of granulomatous. In chronic inflammation there are hyperplasia of parenchyma cells and mesenchyma cells, such as inflammatory polyp in skin or mucosa, inflammatory pseudotumor in liver, lung and spleen. Excessive fibrous proliferation may damage the normal structure of organs and result in cirrhosis during the prolonged inflammation, such as chronic viral hepatitis.
The outcome of inflammation depend on the nature of the injurious agents, immunity of host and cure measure, et al. Most of inflammations are resolutive, only few may progress to the chronic stage if the agents are not removed or the patients have poor immunity. It may happen local or systemic diffusion if there is more agents and strong virulence. Local diffusion of pathogens may through the gap between tissue or native tube. and the systemic diffusion may through lymphatic tube. The pathogens diffuse through vasculature may result in bacteremia, toxemia, septicemia or pyemia. In bacteremia, there is no systemic toxic symptoms, but bacteria can be found in the bloodstream; and in the septicemia, there is a large amount of bacteria in blood, accompanied with toxic symptoms; pyemia is the most severely systemic suppurative infection in which a lot of suppurative thrombus flow in the bloodstream to all organs resulting in metastatic abscess.