Necrosis.pptx definition, types, examples
- 1. Necrosis Dr. S Poude, MD Department of Pathology
- 3. Irreversible injury • Severe injury or persistent injury causes irreversible damage. • Extensive damage to cell membrane • Vacuolisation of mitochondria • Reduced capacity to generate ATP • Necrosis Morphogical changes are : • Nuclear changes and cytoplasmic changes
- 4. Nuclear changes: • Are pathognomonic of necrosis and are of 3 types: • Pyknosis – shrunken,small and hyperchromatic nuclei. • Karyorrhexis – pyknotic nucleus breaks up into fragments • Karyolysis – with time the nuclear fragments slowly fade and ultimately disappear(enzymatic degradation by endonucleases)
- 7. Cytoplasmic changes: • Dense pink cytoplasm ( eosinophilic cytoplasm) • Glassy and homogeneous • Becomes vacuolated and motheaten in appearance • Dead cells may be replaced by large, whorled phospholipid masses called myelin figures
- 8. Necrosis • Is the result of denaturation of intracellular proteins and enzymatic digestion of the lethally injured cell • unable to maintain membrane integrity • their contents often leak out, a process that may elicit inflammation in the surrounding tissue.
- 9. Patterns of Tissue Necrosis • Coagulative necrosis • Liquefactive necrosis • Gangrenous necrosis • Caseous necrosis • Fat necrosis • Fibrinoid necrosis
- 10. Coagulative necrosis • the architecture of dead tissues is preserved for a span of at least some days • the injury denatures enzymes also and so blocks the proteolysis of the dead cells • as a result, eosinophilic, anucleate cells may persist for days or weeks • E.g Renal infarction, Myocardial infarction • Caused by obstruction of blood supply • A localized area of coagulative necrosis is called an infarct
- 14. Liquefactive necrosis • is characterized by digestion of the dead cells, resulting in transformation of the tissue into a liquid viscous mass. • No structural detail can be made out • The necrotic material is frequently creamy yellow because of the presence of dead leukocytes and is called pus • CNS often manifests as liquefactive necrosis • E.g., Bacterial, fungal and ischemic injury of CNS
- 17. Gangrenous necrosis • not a specific pattern of cell death • usually applied to a limb, generally the lower leg, that has lost its blood supply and has undergone necrosis (typically coagulative necrosis) involving multiple tissue planes.
- 18. Caseous necrosis • Most often in foci of tuberculous infection • The term “caseous” (cheeselike) is derived from the friable white appearance of the area of necrosis • microscopic examination, the necrotic area appears as a collection of fragmented or lysed cells and amorphous granular debris
- 19. Caseous necrosis
- 20. Caseous necrosis
- 21. Fat necrosis • The focal areas of fat destruction, typically resulting from release of activated pancreatic lipases into the substance of the pancreas and the peritoneal cavity • The fatty acids, so derived, combine with calcium to produce grossly visible chalky-white areas (fat saponification)
- 22. Fat necrosis
- 23. Fat necrosis
- 24. Fibrinoid necrosis • Special form of necrosis usually seen in immune reactions involving blood vessels • Deposits of these “immune complexes,” together with fibrin that has leaked out of vessels, result in a bright pink and amorphous appearance in H&E stains, called “fibrinoid” (fibrin-like) by pathologists
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