necrosis

3. Necrosis:
 “Necrosis refers to a spectrum of morphologic changes
that follow cell death in living tissue, largely resulting
from progressive degradative action of enzymes on the
lethally injured cells”.

4. Necrosis Apoptosis
1. Cell size: enlarged.
2. Nucleus: Pyknosis-
Karyorrhexis- Karyolysis.
3. Plasma membrane: disrupted
4. Cellular contents: leak out,
enzymatic digestion.
5. Inflammation +++
6. Role: always pathologic.
7. Agarose gel electrophoresis:
diffuse smearing pattern
1. Reduced.
2. Fragmentation.
3. Intact; altered structure.
4. Intact; released into
apoptotic bodies.
5. No.
6. Physiologic/ pathologic.
7. Ladder pattern

5. Why Inflammation around it???
 Necrotic cells are unable to maintain the membrane
integrity and their contents often leak out.
 This will elicit inflammation in the surrounding tissue.

6. Morphology:
 Increased Eosinophilia: attributable to loss of normal
basophilia imparted by RNA in the cytoplasm.
 More glassy homogeneous appearance.
 Cytoplasmic vacuolation: due to digestion of cytoplasmic
organelles –moth eaten appearance.

7.  Nuclear changes: 3 forms--
1. Pyknosis: Nuclear shrinkage and increased basophilia---
DNA is condensed to solid, basophilic mass.
2. Karyorrhexis: Fragmentation of the pyknotic nucleus.
3. Karyolysis: Basophilia of the chromatin may fade—DNAase
activity++
Morphology: ……

8. Dead cells –replaced by:
 Large, whorled phospholipid masses called Myelin figures
 Calcification
 Phospholipids are degraded into fatty acids which undergo
calcification to yield Calcium soaps.
Morphology: ……

9. Electron microscopy:
 Discontinuous plasma membrane
 Dilatation of mitochondria with appearance of Large
amorphous densities
 Amorphous osmiophilic debris
 Aggregates of fluffy material—denatured protein.

10. 1. Coagulative Necrosis
2. Liquefactive Necrosis
3. Caseous Necrosis
4. Enzymatic Fat Necrosis

11. 1. Coagulative Necrosis:
 Implies preservation of basic outline of the coagulated cell
at least for some days.
 Example: Myocardial infarction—acidophilic, coagulated,
anucleate cells persisting for few weeks.
 Ultimately it is removed by phagocytosis by scavenger
leukocytes.

12. 2. Liquefactive Necrosis:
 MC hypoxic death in CNS.
 Transformation of tissue into a liquid viscous mass.
 Seen in fungal/ bacterial infections also.
 Pus: creamy yellow material containing dead white
cells.

13. 3. Caseous Necrosis:
 Most often seen in TUBERCULOSIS.
 Cheesy white- gross appearance of the area of necrosis.
 Amorphous, granular debris enclosed within a distinctive
inflammatory border known as Granulomatous
inflammation.

14. 4. Fat Necrosis:
 Due to release of activated pancreatic lipases—into
pancreatic substances and peritoneal cavity–destroying the
fat.
 MC seen in acute pancreatits.
 Lipases split triglycerides into fatty acids that combine with
calcium to produce grossly visible chalky white areas- FAT
SAPONIFICATION.