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IRREVERSIBLE CELL INJURY- NECROSIS

IRREVERSIBLE CELL INJURY- NECROSIS. Dr. Kiran H S Assisstant Proffessor Pathology,YMC. OVERVIEW. Definition Morphology & mechanism Types of necrosis. Necrosis. Definition. Unregulated form of cell death resulting from damage to cell membranes and loss of ion homeostasis.

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IRREVERSIBLE CELL INJURY- NECROSIS

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  1. IRREVERSIBLE CELL INJURY- NECROSIS Dr. Kiran H S AssisstantProffessor Pathology,YMC

  2. OVERVIEW • Definition • Morphology & mechanism • Types of necrosis

  3. Necrosis Definition • Unregulated form of cell death resulting from damage to cell membranes and loss of ion homeostasis. • Morphological changes of cell death in a living tissue as a result of irreversible injury. • Necrotic cells loose membrane integrity  leakage of cell contents  inflammatory reaction. CELL INJURY

  4. Necrosis • Mechanism:Denaturation of intracellular proteins or enzymatic digestion of lethally injured cell. • Ischemia, exposure to toxins, various infections & trauma. • Autolysis: Enzymatic digestion by cells’ own enzymes stored in lysosomes. • Heterolysis: Enzymatic digestion by enzymes released by inflammatory cells. CELL INJURY

  5. Necrosis Morphology • Cytoplasmic changes. • Nuclear changes. CELL INJURY

  6. Necrosis • Cytoplasmic changes. • Increased eosinophilia: Loss of RNA; bright pink in H/E stain. • Homogenous appearance: Loss of glycogen. • Moth-eaten appearance of cytoplasm: Enzymatic digestion. CELL INJURY

  7. Necrosis • Nuclear changes: • Breakdown of DNA by DNA lysing enzymes. • Three patterns. • Karyolysis: Loss of basophilia; appear pale in H/E. • Pyknosis: Nuclear shrinkage and appear dark (increased basophilia). • Karyorrhexis: Nuclear fragmentation. CELL INJURY

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  10. Necrosis Myelin Figures • End result of cell death. • Laminated structures derived form damaged cell membrane. • Both in reversible and irreversible cell injury; more pronounced in irreversible cell injury. • Intracellular and extracellular. • Phagocytosed or degraded into fatty acids. CELL INJURY

  11. Necrosis Types of Necrosis • Coagulative necrosis. • Liquefactive necrosis. • Gangrenous necrosis. • Caseous necrosis. • Fat necrosis. • Fibrinoid necrosis CELL INJURY

  12. Necrosis 1. Coagulative Necrosis • Intracellular acidosis  denaturation structural and enzymatic proteins  blocking proteolysis  coagulation of cells. • Hypoxic death of all tissues except brain. • Gross: Localized area of coagulative necrosis is called infarct. Affected tissue is firm. • Microscopy: Preservation of basic cell outline. CELL INJURY

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  15. Necrosis 2. Liquefactive Necrosis • Complete digestion of dead cells liquid viscous mass ; creamy yellow pus  abscess. • Bacterial infection, and hypoxic cell death of brain. • Bacterial infection  accumulation of inflammatory cells  release enzymes  cell digestion. • Gross: Affected tissue is soft. • Microscopy: Amorphous debris, no cell outline, inflammatory cells. CELL INJURY

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  17. Necrosis 3. Gangrenous necrosis • Gross feature of extensive necrosis. • Dry gangrene: Ischemia  loss of blood supply  coagulative necrosis. • Wet gangrene: Superimposed bacterial infection on dry gangrene  degradative enzymes released by bacteria and WBCs  liquefactive necrosis. CELL INJURY

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  23. Necrosis 4. Caseous Necrosis • Type of coagulative necrosis. • Seen in tuberculosis. • Caseous = Cheesy (gross). • Amorphous granular debris of coagulated cells and granulomatous reaction. CELL INJURY

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  27. Necrosis 4. Fat Necrosis • Localized area of fat destruction. • Acute pancreatitis and breast trauma. • Acute pancreatitis: Acute inflammation of pancreas  release of activated pancreatic lipase into peritoneum  liquefaction of fat cells  release of fatty acids  combine with calcium. • Gross: Chalky white areas of calcification. • Microscopy: Necrotic fat cells, calcium deposits, inflammatory infiltration. CELL INJURY

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  29. 5. Fibrinoid necrosis • Special form of necrosis, usually seen in immune reactions involving blood vessels. • Due to antigen antibody complex deposition on the walls of arteries. • Vasculitis syndromes.

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