1. NECROSIS -Dr Sowmya Srinivas

2. DEFINITION NECROSIS NECROSIS Its an irriversible injury produced by enzymatic digestion of dead cellular elements APOPTOSIS Its a vital process that helps eliminate unwanted cells-an internally programmed series of events causing cell death

3. MECHANISM

4. MORPHOLOGY OF NECROSIS : 1.Cellular swelling or rupture 2.Denaturation and coagulation of cytoplasmic proteins 3.Breakdown of cell organelles 4.Breakdown of nuclear DNA

5. PATTERNS OF NECROSIS IN TISSUES OR ORGANS As a result of cell death the tissues or organs display one of these six macroscopic changes: 1. 1.Coagulative necrosis 2. 2.Liquefactive necrosis 3. 3.Caseous necrosis 4. 4.Fat necrosis 5. 5.Gangrenous necrosis 6. 6.Fibrinoid necrosis

6. PATTERNS OF NECROSIS IN TISSUES OR ORGANS 1.Coagulative necrosis: the outline of the dead cells are maintained and the tissue is somewhat firm. Example: Myocardial infarction, liver, kidney, thermal burns 2.Liquefactive necrosis: the dead cells undergo disintegration and affected tissue is liquefied. Example: Brain

8. GROSS - NECROSIS Affected areas look white, grey or yellow in colour. Affected areas look white, grey or yellow in colour. Have a cooked meat appearance. Have a cooked meat appearance. Sharply demarcated (by red zone) from healthy tissue. Sharply demarcated (by red zone) from healthy tissue. In case of gangrene the area is green, orange or black (iron sulphide) In case of gangrene the area is green, orange or black (iron sulphide)

9. MICROSCOPY - NECROSIS The microscopic changes of necrosis vary with the type of necrosis. Some general changes of necrosis in the cytoplasm are:  Eosinophilia: The cytoplasm stains darker red in colour.  Swelling and vacuolation: The cells are swollen and contain different types of vacuoles.  Changes in the nucleus: The nucleus may show condensation (Pyknosis), fragmentation (karyorrhexis) and may disappear (karyolysis).

10. COAGULATIVE NECROSIS  Most common type of necrosis.  Architectural outlines persist but cellular details are lost.  Type of tissue can be recognized.  Denaturation (coagulation) of structural and enzymic proteins blocks proteolysis.

11. CAUSES OF COAGULATIVE NECROSIS Ischemia due to thrombosis/ embolism as in infarcts. Ischemia due to thrombosis/ embolism as in infarcts. Bacterial toxins e.g. Fusobacterium necrophorum in livers in cattle. Bacterial toxins e.g. Fusobacterium necrophorum in livers in cattle. Muscular dystrophy due to deficiency of selenium and vit. E in cattle and sheep. Muscular dystrophy due to deficiency of selenium and vit. E in cattle and sheep. Necrosis of renal epithelium due to poisoning from mercuric salts. Necrosis of renal epithelium due to poisoning from mercuric salts.

12. Gross appearance: Necrotic area is firm, opaque with cooked meat appearance. Necrotic area is firm, opaque with cooked meat appearance. It is sharply demarcated from the healthy areas. It is sharply demarcated from the healthy areas. Microscopic appearance: Architectural outlines are present; cellular details are lacking. Architectural outlines are present; cellular details are lacking.Result: Dead tissues remain in the body for a long period, ultimately removed by macrophages. Dead tissues remain in the body for a long period, ultimately removed by macrophages.

13. GROSS – COAGULATIVE NECROSIS

14. NORMAL CARDIAC MUSCLE

15. MICROSCOPIC VIEW

16. COAGULATIVE NECROSIS

18. MICROSCOPIC VIEW

21. CASEOUS NECROSIS Dead tissue is converted into a homogenous, granular mass resembling cottage cheese. Cause: Associated with lesions of Mycobacterium tuberculosis, the cause of caseous lymphadinitis.

22. Gross appearance: The area of necrosis is amorphous, granular, friable, white- grey resembling cottage cheese. The area of necrosis is amorphous, granular, friable, white- grey resembling cottage cheese. The caseous mass is enclosed within a connective tissue capsule. Microscopic appearance: The necrotic tissue is amorphous, granular mass enclosed inside a zone of granulomatous inflammation, containing macrophages. No architectural or cellular details are seen. Calcification commonly occurs in the necrotic areas. The necrotic tissue is amorphous, granular mass enclosed inside a zone of granulomatous inflammation, containing macrophages. No architectural or cellular details are seen. Calcification commonly occurs in the necrotic areas.

23. GROSS – CASEOUS NECROSIS

24. MICROSCOPY – CASEOUS NECROSIS

26. LIQUEFACTIVE NECROSIS Rate of dissolution of the necrotic cells is faster than the rate of repair. Usually results in an abscess secondary to bacterial infection. Rate of dissolution of the necrotic cells is faster than the rate of repair. Usually results in an abscess secondary to bacterial infection. Hydrolysis of dead tissues or cells rapidly destroyed by lysosomal enzymes from neutrophilic leukocytes (i.e., bacterial infections), or clostridia or snake poison. Hydrolysis of dead tissues or cells rapidly destroyed by lysosomal enzymes from neutrophilic leukocytes (i.e., bacterial infections), or clostridia or snake poison. Liquefactive necrosis that is caused by neutrophilic leukocytes is called pus. Liquefactive necrosis that is caused by neutrophilic leukocytes is called pus.

27. LIQUEFACTIVE NECROSIS