Acute Inflammation PDF

Acute inflammation DEFINITION Inflammation is a response of vascularized tissues to infections and tissue damage The steps of the inflammatory response can be remembered as the five Rs (1) Recognition of the injurious agent, (2) Recruitment of leukocytes, (3) Removal of the agent, (4) Regulation (co...

Acute inflammation DEFINITION Inflammation is a response of vascularized tissues to infections and tissue damage The steps of the inflammatory response can be remembered as the five Rs (1) Recognition of the injurious agent, (2) Recruitment of leukocytes, (3) Removal of the agent, (4) Regulation (control) of the response, and (5) Resolution (repair). Types of inflammation Acute Chronic Cardinal signs of inflammation (5): Redness (rubor), swelling (tumor), heat (calor), pain (dolor), and loss of function (functio laesa), Acute Inflammation Acute inflammation is a rapid host response that serves to deliver leukocytes and plasma proteins, such as antibodies, to sites of infection or tissue injury. CAUSES OF INFLAMMATION Infections (bacterial, viral, fungal, parasitic) Tissue necrosis Foreign bodies Immune reactions Acute inflammation components (1) alterations in vascular caliber that lead to an increase in blood flow (2) structural changes in the microvasculature that permit plasma proteins and leukocytes to leave the circulation (3) emigration of the leukocytes from the microcirculation REACTIONS OF BLOOD VESSELS IN ACUTE INFLAMMATION 1- Changes in the flow of blood 2- Permeability of vessels. Vasodilation is one of the earliest manifestations of acute inflammation; sometimes it follows a transient vasoconstriction lasting a few seconds Edema denotes an excess of fluid in the interstitial tissue or serous cavities; it can be either an exudate or a transudate. Pus, a purulent exudate, is an inflammatory exudate rich in leukocytes (mostly neutrophils), the debris of dead cells and, in many cases, microbes. An exudate is an extravascular fluid that has a high protein concentration, contains cellular debris, and has a high specific gravity a transudate is a fluid with low protein content (most of which is albumin), little or no cellular material, and low specific gravity. Responses of Lymphatic Vessels In inflammation, lymph flow is increased to help drain edema fluid that accumulates because of increased vascular permeability. REACTIONS OF LEUKOCYTES IN INFLAMMATION A critical function of inflammation is to deliver leukocytes to the site of injury and to activate the leukocytes to eliminate the offending agents. The processes involving leukocytes in inflammation consist of: 1- Their recruitment from the blood into extravascular tissues, 2- Recognition of microbes and necrotic tissues, and 3- Removal of the offending agent. Chemotaxis of Leukocytes After exiting the circulation, leukocytes emigrate in tissues toward the site of injury by a process called chemotaxis which is defined as locomotion oriented along a chemical gradient. Both exogenous and endogenous substances can act as chemoattractants. The most common exogenous agents are bacterial products, Phagocytosis. Phagocytosis involves three sequential steps : (1) recognition and attachment of the particle to be ingested by the leukocyte; (2) its engulfment, with subsequent formation of a phagocytic vacuole; and (3) killing or degradation of the ingested material. Outcomes of Acute Inflammation Complete resolution inflammatory reactions, once they have succeeded in neutralizing and eliminating the injurious stimulus, should end with restoration of the site of acute inflammation to normal. Progression of the response to chronic inflammation. Acute to chronic transition occurs when the acute inflammatory response cannot be resolved, as a result of either the persistence of the injurious agent or some interference with the normal process of healing. Healing by connective tissue replacement (fibrosis). Morphologic Patterns of Acute Inflammation SEROUS INFLAMMATION Serous inflammation is marked by the exudation of cell-poor fluid FIBRINOUS INFLAMMATION A fibrinous exudate develops when the vascular leaks are large or there is a local procoagulant stimulus. SUPPURATIVE OR PURULENT INFLAMMATION ; ABSCESS Purulent inflammation is characterized by the production of pus, an exudate consisting of neutrophils, the liquefied debris of necrotic cells, and edema fluid. ULCERS An ulcer is a local defect, or excavation, of the surface of an organ or tissue that is produced by the sloughing (shedding) of inflamed necrotic tissue. SEROUS INFLAMMATION FIBRINOUS INFLAMMATION SUPPURATIVE OR PURULENT INFLAMMATION ; ABSCESS ULCER Systemic Effects of Inflammation Fever Acute-phase proteins Leukocytosis