Necrosis

NECROSIS

• Necrosis is defined as localised area of tissue death which later leads to degradation of tissues by hydrolytic enzymes liberated from dead cells.
• Based on morphology 5 types of necrosis-

1. Coagulative necrosis-

• Most common type of necrosis caused by sudden cessation of blood flow.
• It effects- heart, kidney, spleen (except brain).
• Underlying tissue architecture is preserved.
• Coagulative necrosis is characteristics of infarcts in all solid organs (mainly heart).
• Hallmark of coagulative necrosis is conversion of normal cells into their tombstones.
• The cell injury causes denaturation of protein.

 

2. Liquefactive necrosis-

• Liquefactive or colliquative necrosis occurs due to lysosomal permeability and enzymes of leukocytes digest the tissue transforming the tissue into liquid viscous mass.
• Tissue architecture is lost.
• Examples are- Infarct brain and abscess cavity.

 

3. Caseous necrosis-

• Caseous means cheese like appearance.
• It is found in the centre of foci of tuberculous infections & histoplasmosis.
• It has features of both coagulative & liquefactive necrosis.

  

4. Fat necrosis-

• Fat necrosis refers to cell death in fat rich organs of the body.
• Mesentric fat necrosis due to acute pancreatitis as there is liberation of pancreatitic lipases resulting in necrosis of pancreas & peritoneal cavity.
• Traumatic fat necrosis of the breast.
• The released fatty acids combined with calcium gives a chalky white appearance.

 

5. Fibrinoid necrosis-

• Fibrinoid necrosis is a special form of necrosis in immune reactions in which antigen and antibodies are deposited on the walls of arteries.
• It is seen in vasculitis & malignant hypertension.
• Seen in sarcoidosis.

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