Inflammation: Immune Response to Tissue Injury or Infection

MEDICAL ANIMATION TRANSCRIPT: Inflammation is a local immune response to tissue injury or infection, experienced as heat, redness, edema, pain, and loss of function. Immediately after injury, inflammation begins with brief vasoconstriction of the local blood vessels to reduce blood loss and formation of a clot to stop the bleeding. Then, stimulated by cell injury and death, local cells release vasoactive chemicals, such as prostaglandins and histamine to dilate local blood vessels leading to increased blood flow to the area. These chemicals also cause endothelial cells in small blood vessels to contract, opening spaces between them. This increased capillary permeability allows fluids and proteins to pass from the blood into the tissue. Next, during a multi-stage process called chemotaxis, circulating immune cells called neutrophils move out of the blood vessels to the site of injury and destroy pathogens and damaged cells. Chemotaxis begins when cells at the injury site release messenger molecules called chemoattractants, which cause local endothelial cells and circulating neutrophils to stick together. Next, in a process called diapedesis, neutrophils squeeze through the endothelial gaps. The neutrophils migrate to the injury site by following a chemotactic gradient. Upon arrival, the neutrophils encounter bacteria, engulf them and digest them in a process called phagocytosis. After destruction of the bacteria and removal of cellular waste, tissue repair begins when locally produced growth factors cause local fibroblasts to begin dividing rapidly and secreting large quantities of collagen to reinforce the wound. Anti-inflammatory drugs inhibit inflammation by blocking production of inflammatory chemicals. The most common drugs for inflammation are non-steroidal anti-inflammatory drugs, or NSAIDS, such as aspirin and ibuprofen. They contain an enzyme called cyclooxygenase or COX, that inhibits the production of prostaglandins and several other inflammatory chemicals. Thus, reducing vasodilation, edema, and pain associated with inflammation.

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ANM11028