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Unformatted text preview: Pathology 3-Inflammation • Where there is necrosis, inflammation occurs; end of inflammation=beginning of healing • Tissue injury stimulates a series of reactions to occur at the site of injury- inflammatory reaction; purpose: • 1. To destroy or limit the spread of the injurious agent • 2. To allow for repair or replacement of the damaged tissues • Inflammation= characteristic response of living tissues to an injury: • A) inflammation is a dynamic, ever changing process consisting of a chain of reactions which succeed or overlap eachother; it is NOT a static situation • B) the injury must be non-lethal . If the injury is of such severity to destroy the tissue at the outset, no inflammatory response can occur in that time; requires energy and oxygen from cells; require that the individual can respond; need blood flow and oxygen for an immune response • C) the inflammatory response is non-specific . Many diverse injuries can cause inflammation and the initial stages of the inflammatory action are identical in almost all of the tissues, irrespective of the type of injury. The intensity, duration and outcome of the inflammatory reaction are modified by factors pertaining to the host as well as to the injurious insult; it is stereotyped and very predictable • Causes of inflammatory reaction (essentially the same stuff as cell injury and cell death): • 1. Infection : ex invasion and multiplication within tissues by organisms; bacteria, fungi, viruses and protozoa—cause damage by release of toxins which directly destroy host cells • **do not confuse inflammation with infection; an infection almost always will cause an inflammatory response; however the etiologies of an inflammatory response are diverse; usually a relatively large inflammatory reaction will occur in response to an infection; infection≠inflammation..it is a type of inflammation • 2. Trauma: penetrating injury (stab wound, wood sliver), blunt trauma, thermal injury (excessive heat or cold), chemical injury (acid or alkali) • 3. Immunologically mediated: humoral or cellular, allergies, vaccinations • 4. Loss of blood supply (ischemia); decreased O2 • Inflammation can be divided into vascular and cellular events; both are mediated by chemical factors but both events actually occur concomitantly Triangle of Inflammation: Cells, Vessels (where takes place), Chemical Mediators (makes things happen) → all happens at once 1. Vascular Events: • Lewis’s Triple Response: 1. Pallor (pale—very brief); 2. Redness; 3. swelling • A)Immediately following injury= transient vaso constriction of arterioles; mediated by nerves to the smooth muscle and within the arteriolar walls (neurological response); brief—lasts for 5 mins→makes area pale (less blood flow to site of injury • Microcirculation=basic unit • B)Next: vaso dilation of venules, capillaries, arterioles (more hemodynamically important); opening of precapillary sphincters of arterioles, opening up of...
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- Spring '11
- Pathology, cells, inflammatory reaction