An inflammation may be triggered by several mechanisms including noxious physical or chemical agents, accumulated metabolic products, immunologic or infectious tissue injury, or tissue necrosis. During an acute inflammation, there are hemodynamic changes like initial vasoconstriction followed by vasodilation increasing vascular permeability. This allows fluid and proteins to accumulate in tissues (edema) and neutrophils to migrate from blood vessels to the site of injury. Neutrophils play an important role by adhering to endothelial cells through a process involving selectins and integrins.