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Chapter 4 Injury, Inflammation, and Repair

Chapter 4 Injury, Inflammation, and Repair. Review of Structure and Function. The body is capable of undergoing dynamic changes to carry out body functions. Each component of a cell carries out a specific, necessary function. Major Cell Types. Epithelial cells Connective tissue cells

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Chapter 4 Injury, Inflammation, and Repair

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  1. Chapter 4 Injury, Inflammation, and Repair

  2. Review of Structure and Function • The body is capable of undergoing dynamic changes to carry out body functions. • Each component of a cell carries out a specific, necessary function.

  3. Major Cell Types • Epithelial cells • Connective tissue cells • Nerve cells • Muscle cells

  4. Events Following Injury • Necrosis or sublethal cell injury • Death or damage of cells due to injury • Inflammation • The vascular and cellular response attempting to limit damage and remove necrotic tissue

  5. Events Following Injury • Repair • The body’s attempt to replace dead cells

  6. Necrosis vs. Sublethal • Necrosis is the irreversible death of the cell • Sublethal injury indicates the cell is capable of at least some recovery.

  7. Acute Injury and Necrosis • The most common cause of acute injury is a reduced level of oxygen. • Cells that are very active require more oxygen, and will suffer ill effects first. • Localized hypoxia due to poor blood flow (not decreased oxygen levels) is called ischemia. If this becomes more severe, ischemia progresses to infarct.

  8. Causes of ischemia or necrosis • Thrombus • Embolus • Trauma • Infections

  9. Causes of ischemia or necrosis • Immunologic Reactions • Coagulation, liquefaction, caseous, gangrenous, and enzymatic fat necrosis

  10. Chronic Injury • Chronic injury may cause atrophy or accumulation of material within cells. • Atrophy • Senile • Disuse • Pressure • Denervation • Endocrine

  11. Chronic Injury • Accumulation • Fatty Change • Adiposity • Glycogen Storage • Hyaline • Metastatic Calcification • Hemosiderosis • Hemochromatosis

  12. Acute Inflammation • Vascular response: Increased blood flow to the injured area, and the vasculature becomes more permeable. • Cellular response: Movement of leukocytes, predominantly neutrophils and monocytes from the blood into the tissue.

  13. Chemical Mediators • The inflammatory reaction is initiated by local factors in the injured tissue • Histamine • Vasoactive amines

  14. Chemical Systems • There are three chemical systems at work together during the inflammatory reaction • Kinin system • Complement system • Coagulation system

  15. Chronic Inflammation • Chronic inflammation causes histologic changes different from acute inflammation.

  16. Granulomatous Inflammation • Characterized by focal collections of closely packed, plump macrophages, it is in response to indigestible organisms. • The object is too large to be broken down, so macrophages engulf the offender to keep it from moving elsewhere. • Examples include: TB, fungal infections, and sarcoidosis

  17. Transudates and Exudates • Transudate • Caused by increased hydrostatic pressure or decreased osmotic pressure • These have a low protein count • Exudate • Caused by increased oncotic pressure • These have a high protein count

  18. Repair • Regeneration • This is the desired repair, as replacement of destroyed tissue is with similar tissue, and normal function is restored.

  19. Repair • Fibrous connective tissue repair • This is less desired, as the damaged area is replaced with fibrous tissue, and normal function is not restored. • The goal of this repair is to provide a bridge across the damaged area.

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