Definition Of Inflammation: Acute Inflammation PDF

College of Medicine – ‫كلية الطب‬ Definition Of Inflammation: Acute Inflammation Dr. Saly rashad  Upon completion of this lecture, students should be abl...

College of Medicine – ‫كلية الطب‬ Definition Of Inflammation: Acute Inflammation Dr. Saly rashad  Upon completion of this lecture, students should be able to: ❑ Define inflammation. College of Medicine – ‫كلية الطب‬ ❑ Have good knowledge about the types and functions of the various inflammatory cells including their role in both acute and chronic inflammation. ❑ Compare between acute and chronic inflammation. ❑ Recognize the cardinal signs of inflammation. ❑ Understands the vascular changes occurring as a response to tissue injury.  ❑ Describe the sequence of vascular changes in acute inflammation (vasodilation, increased permeability) and their purpose College of Medicine – ‫كلية الطب‬ ❑ Know the mechanisms of increased vascular permeability ❑ Appreciate the importance of fluid production in inflammation including the differences between exudates and transudates ❑ Compare normal capillary exchanges with exchange during inflammatory response ❑ Define the terms edema, transudate, and exudate  ❑ Inflammation is a vascular and cellular response to injury. College of Medicine – ‫كلية الطب‬ Inflammation Processes: ❑ Exudation of fluid from vessels ❑ Attraction of leukocytes to the injury. Leukocytes engulf and destroy bacteria, tissue debris, and other particulate material ❑ Activation of chemical mediators ❑ Proteolytic degradation of extracellular debris ❑ Restoration of injured tissue to its normal structure & function  Cardinal signs of Inflammation: Redness: caused by dilation of vessels. College of Medicine – ‫كلية الطب‬ Pain: due to increased pressure exerted by the accumulation of interstitial fluid and to mediators (bradykinin). Heat: caused by increased blood flow. Swelling: due to an extravascular accumulation of fluid. Loss of function.  Causes of Inflammation: ❑ Infection College of Medicine – ‫كلية الطب‬ ❑ Trauma ❑ Physical injury from thermal extremes or from ionizing radiation. ❑ Chemical injury. ❑ Immunologic injury.  Neutrophils: Neutrophils are the most prominent inflammatory cells in acute inflammation. College of Medicine – ‫كلية الطب‬ Important causes of neutrophilia include bacterial infections. The function of PMN in inflammation is: ❑ Phagocytosis of the microorganisms. ❑ Engulfment of antigen-antibody complex & nonmicrobial material.  Macrophage:  In acute inflammation, neutrophils are replaced mainly by macrophages and are also prominent cells in College of Medicine – ‫كلية الطب‬ chronic inflammation.  Macrophages are longer lived and are capable of dividing and proliferating within the inflamed tissue.  Macrophages are capable of engulfing larger particles.  Lymphocytes:  Lymphocytes are the most prominent inflammatory College of Medicine – ‫كلية الطب‬ cells in many viral infections.  Lymphocytes along with macrophages and plasma cells are the most prominent cells in chronic inflammation.  Plasma cells develop from B lymphocytes.  Lymphocytes are responsible for antibody production, direct cell-mediated killing of virus-infected cells, and regulation of the immune response.  Eosinophils:  Eosinophils are the predominant inflammatory cells in allergic reactions and parasitic infestations College of Medicine – ‫كلية الطب‬ Mast cells: Mast cells have a major role in hypersensitivity reactions. College of Medicine – ‫كلية الطب‬   Acute inflammation is a rapid response to injury that is designed to deliver leukocytes and plasma proteins to sites of injury College of Medicine – ‫كلية الطب‬  Short duration  A predominantly neutrophilic leukocyte accumulation Acute inflammation has two major components: ❑ Vascular changes Vasodilation Increased vascular permeability ❑ Cellular events  Changes in Vascular Caliber and Flow  Occurrence of arteriolar vasodilation results in : locally increased blood flow College of Medicine – ‫كلية الطب‬  The vascular expansion is the cause of the redness and warmth seen in acute inflammation.  As the microvasculature becomes more permeable, protein- rich fluid moves into the extravascular tissues.  The extravascular fluid movement causes: College of Medicine – ‫كلية الطب‬  Increasing blood viscosity  slowing the circulation  These changes leads to slowly flowing blood (stasis)  As stasis develops, leukocytes accumulate along the vascular endothelial surface (margination)  Increased Vascular Permeability  Arteriolar vasodilation and increased volume of blood flow a rise in intravascular hydrostatic pressure movement of College of Medicine – ‫كلية الطب‬ fluid from capillaries into the tissues (transudate)  Transudate contains little protein.  Increasing vascular permeability allows the movement of protein-rich fluid and even cells (exudate) into the interstitium  The loss of protein-rich fluid into the interstitium Reduces the intravascular osmotic pressure Increases the osmotic pressure of the interstitial fluid   The net result is outflow of water and ions into the College of Medicine – ‫كلية الطب‬ extravascular tissues.  Fluid accumulation in extravascular spaces is called edema. College of Medicine – ‫كلية الطب‬  Retraction of endothelial cells: College of Medicine – ‫كلية الطب‬ o There is opening of inter-endothelial spaces o It is produced by histamine, bradykinin, leukotrienes Endothelial injury: o There is endothelial cell necrosis and detachment  Increased transport of fluids and proteins through College of Medicine – ‫كلية الطب‬ the endothelial cell (transcytosis) o Macromolecules are captured in vesicles on one side of the cell o drawn across the cell o ejected on the other side College of Medicine – ‫كلية الطب‬ Increased permeability of small blood vessels in inflammation is mediated by several mechanisms, the most important of which are illustrated here. A, Formation of gaps between endothelial cells. B, Direct injury of endothelial cell. Endothelial cell injury may be caused by a variety of chemicals but also by leukocytes. C, Increased transcytosis. College of Medicine – ‫كلية الطب‬ Macrophage Neutrophil eosinophil