Necrosis

The spectrum of morphological changes that leads to cell death within a living tissue
Cell death due to an irreversible cell injury

1. Necrosis Quick Review

2. N ecrosis The spectrum of morphological changes that leads to cell death within a living tissue Cell death due to an irreversible cell injury

3. Main processes occur in necrosis Degeneration of intracellular proteins Enzymatic digestion of cells

4. Early morphological changes in necrosis: Cytoplasm Increased eosinophilia Glassy homogenous appearance (due to loss of glycogen ) Vacuolated cytoplasm ( moth-eaten appearance)

5. Early morphological changes in necrosis: Nucleus Pyknosis - nuclear shrinkage & condensation Karyorrhexis - fragmentation Karyolysis - chromatin fades

6. Types of necrosis Liquefactive necrosis Coagulative necrosis Caseous necrosis Fat necrosis Gangrene necrosis Tumour necrosis Fibrinoid necrosis

7. Coagulative necrosis

8. Coagulative necrosis Default pattern of necrosis Associated with ischemia or hypoxia In every organ in the body except the brain

9. Coagulative necrosis Macroscopic appearance Tissue is firm Architecture is maintained for few days after cell death Microscopic appearance Preserved cell outlines without nuclei

10. Coagulative necrosis

11. Coagulative necrosis

12. Coagulative necrosis Renal tubule

13. Coagulative necrosis : Examples Myocardial infarction Renal infarction

14. Liquefactive necrosis

15. Liquefactive necrosis Due to the infection, inflammatory cells accumulate Secrete lysosomal hydrolytic enzymes Cells become lysed/ digested/ liquefied Digested tissue is removed by phagocytosis

16. Liquefactive necrosis Macroscopic appearance Tissue is in a  liquid form Sometimes creamy yellow because of pus formation Microscopic appearance Lots of neutrophils Cell debris

17. Liquefactive necrosis

18. Liquefactive necrosis

19. Liquefactive necrosis: Examples Focal bacterial & fungal infections Hypoxic cell death in the CNS

20. Fat necrosis

21. Fat necrosis Damaged cells release digestive enzymes Break down lipids Generate free fatty acids

22. Fat necrosis Macroscopic appearance Chalky white areas Microscopic appearance Annucleated adipocytes Basophillic calcium deposits

23. Fat necrosis

24. Fat necrosis: Example Pancreatitis

25. Caseous necrosis

26. Caseous necrosis A unique type of cell death seen with tuberculosis Rare otherwise

27. Caseous necrosis Macroscopic appearance White, soft, cheese like appearance Microscopic appearance A uniformly eosinophilic center ( necrosis) surrounded by a collar of lymphocytes & activated macrophages (giant cells, epithelioid cells ). “Granuloma”

28. Caseous necrosis: Example Tuberculosis

29. Caseous necrosis

30. Caseous necrosis

31. Fibrinoid necrosis

32. Fibrinoid necrosis Immune complex and fibrin deposition in vessel wall

33. Fibrinoid necrosis Macroscopic appearance Usually no gross changes Microscopic appearance Fibrin deposition within vessel wall, pinkish red

34. Fibrinoid necrosis

35. Fibrinoid necrosis: Example Autoimmune vascular disease polyarteritis nodosa

36. Gangrene necrosis

37. Gangrene necrosis

38. Gangrene necrosis Macroscopic appearance Skin dead and black Microscopic appearance Initially, as in coagulative necrosis – dry gangrene If there is an infection, as in liquefactive necrosis – wet gangrene

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