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.

4. Major Cell Types Epithelial cells Connective tissue cells Nerve cells Muscle cells

5. 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

6. Events Following Injury Repair –The body’s attempt to replace dead cells

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

9. 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.

10. Causes of ischemia or necrosis Thrombus Embolus Trauma Infections

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

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

13. Chronic Injury Accumulation –Fatty Change –Adiposity –Glycogen Storage –Hyaline –Metastatic Calcification –Hemosiderosis –Hemochromatosis

14. 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.

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

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

20. Chronic Inflammation Chronic inflammation causes histologic changes different from acute inflammation.

22. 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

23. 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

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

25. 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.