IRREVERSIBLE CELL INJURYNECROSIS Dr Kiran H S Assisstant

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IRREVERSIBLE CELL INJURYNECROSIS Dr. Kiran H S Assisstant Proffessor Pathology, YMC

IRREVERSIBLE CELL INJURYNECROSIS Dr. Kiran H S Assisstant Proffessor Pathology, YMC

OVERVIEW �Definition �Morphology & mechanism �Types of necrosis

OVERVIEW �Definition �Morphology & mechanism �Types of necrosis

Necrosis Definition �Unregulated form of cell death resulting from damage to cell membranes and

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. 30 -Oct-20 CELL INJURY 4

Necrosis �Mechanism: Denaturation of intracellular proteins or enzymatic digestion of lethally injured cell. �Ischemia,

Necrosis �Mechanism: Denaturation of intracellular proteins or enzymatic digestion of lethally injured cell. �Ischemia, exposure to toxins, various infections & trauma. ü Autolysis: Enzymatic digestion by cells’ own enzymes stored in lysosomes. ü Heterolysis: Enzymatic digestion by enzymes released by inflammatory cells. 30 -Oct-20 CELL INJURY 5

Necrosis Morphology �Cytoplasmic changes. �Nuclear changes. 30 -Oct-20 CELL INJURY 8

Necrosis Morphology �Cytoplasmic changes. �Nuclear changes. 30 -Oct-20 CELL INJURY 8

Necrosis �Cytoplasmic changes. ü Increased eosinophilia: Loss of RNA; bright pink in H/E stain.

Necrosis �Cytoplasmic changes. ü Increased eosinophilia: Loss of RNA; bright pink in H/E stain. ü Homogenous appearance: Loss of glycogen. ü Moth-eaten appearance of cytoplasm: Enzymatic digestion. 30 -Oct-20 CELL INJURY 9

Necrosis � Nuclear changes: ü Breakdown of DNA by DNA lysing enzymes. ü Three

Necrosis � Nuclear changes: ü Breakdown of DNA by DNA lysing enzymes. ü Three patterns. 1. 2. Karyolysis: Loss of basophilia; appear pale in H/E. 3. Karyorrhexis: Nuclear fragmentation. Pyknosis: Nuclear shrinkage and appear dark (increased basophilia). 30 -Oct-20 CELL INJURY 10

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Necrosis Myelin Figures �End result of cell death. �Laminated structures derived form damaged cell

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. 30 -Oct-20 CELL INJURY 14

Necrosis Types of Necrosis 1. Coagulative necrosis. 2. Liquefactive necrosis. 3. Gangrenous necrosis. 4.

Necrosis Types of Necrosis 1. Coagulative necrosis. 2. Liquefactive necrosis. 3. Gangrenous necrosis. 4. Caseous necrosis. 5. Fat necrosis. 6. Fibrinoid necrosis 30 -Oct-20 CELL INJURY 16

Necrosis 1. Coagulative Necrosis �Intracellular acidosis denaturation structural and enzymatic proteins blocking proteolysis coagulation

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. 30 -Oct-20 CELL INJURY 17

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Necrosis 2. Liquefactive Necrosis �Complete digestion of dead cells liquid viscous mass ; creamy

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. 30 -Oct-20 CELL INJURY 20

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Necrosis 3. Gangrenous necrosis �Gross feature of extensive necrosis. ü Dry gangrene: Ischemia loss

Necrosis 3. Gangrenous necrosis �Gross feature of extensive necrosis. ü Dry gangrene: Ischemia loss of blood supply coagulative necrosis. ü Wet gangrene: Superimposed bacterial infection on dry gangrene degradative enzymes released by bacteria and WBCs liquefactive necrosis. 30 -Oct-20 CELL INJURY 23

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Necrosis 4. Caseous Necrosis �Type of coagulative necrosis. �Seen in tuberculosis. �Caseous = Cheesy

Necrosis 4. Caseous Necrosis �Type of coagulative necrosis. �Seen in tuberculosis. �Caseous = Cheesy (gross). �Amorphous granular debris of coagulated cells and granulomatous reaction. 30 -Oct-20 CELL INJURY 29

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Necrosis 4. Fat Necrosis �Localized area of fat destruction. �Acute pancreatitis and breast trauma.

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. 30 -Oct-20 CELL INJURY 34

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30 -Oct-20 CELL INJURY 36

5. Fibrinoid necrosis �Special form of necrosis, usually seen in immune reactions involving blood

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.