2. NECROSIS
Def: It is defined as focal death along with degradation of tissue by hydrolytic
enzymes liberated by cells and is accompanied by inflammation.
Causative agents:
• Hypoxia
• Chemical and physical agents
• Microbial agents
• Immunological injury
3. MORPHOLOGY
Cytoplasm
• Increased eosinophilia due to loss of RNA
• Glassy homogenous appearance due to loss of glycogen particles
• Vacuolated or moth eaten appearance
• Myelin figures
• Electron microscopy- discontinuities in plasma & organelle membranes, marked dilation of
mitochondria ,amorphous densities
4. NUCLEUS
Pyknosis
• Nuclear shrinkage due to condensation of nuclear chromatin
Karyolysis
• Chromatin fades- loss of DNA due to enzymaticdegradation by
endonucleases
Karyorrhexis
• Pyknotic nucleus undergo fragmentation
5. COAGULATIVE NECROSIS
• Most common type due to ischaemia
• Organs- heart, kidney, spleen
• Grossly- foci of necrosis
• Early pale, firm & slightly swollen and shrunken
• Later yellowish softer & shrunken
• Microscopy- Conversion of normal cells into their tombstones i.e cell outline preserved but
nuclear details lostCells swollen, more eosinophilic with nuclear changes
6.
7.
8. LIQUEFACTIVE NECROSIS
• It is characterised by digestion of the dead cells, resulting in transformation of the tissues into
liquid viscous mass
• Seen in focal bacterial and fungal infections
• Examples- infarct brain, abscess cavity
• Grossly- affected area is soft with liquefied centre containing necrotic debris, cyst wall
• Microscopically- cystic space shows necrotic cell debris and macrophages
9.
10. CASEOUS NECROSIS
Combines featues of coagulative and liquefactive necrosis
Example:
• tuberculosis lesions
• fungal infections
• Coccidioidomycosis
• Blastomycosis
• Histoplasmosis
Gross- Dry cheese, soft, granular and yellowish
Microscopy- necrosed foci are structureless eosinophilic with
granular debris surrounded inflammatory cells (granulomas)
11.
12.
13. FATTY NECROSIS
• Focal area of fat destruction, resulting from release of pancreatic
lipases.
• Traumatic fat necrosis
• Gross- fat necrosis seen as yellowish white and firm deposits, chalky
white appearance.
• Microscopy-Necrosed fat cells have cloudy appearance & are
surrounded by inflammatory reaction.
14.
15. FIBRINOID NECROSIS
• It is characterised by depostion of fibrin like material
which has staining properties of fibrin•
• Seen in immunological tissue injury , immune
complex vasculitis, autoimmune diseases, arthus
reaction), Arterioles in hypertension and peptic ulcer
16.
17.
18. GANGRENE
• Gangrene is a form of necrosis of tissue with superadded
putrefaction
• Usually coagulative type due to ischaemia
Example-
• gangrene of bowel
• gangrene of limb
• Gangrenous or necrotising inflammation- gangrene lung, gangrenous
appendicitis
Types-
• Dry gangrene
• Wet gangrene
19. DRY GANGRENE
It begins in the distal part of a limb due to ischaemia.
Examples- dry gangrene in toes & feet of an old person due to arteriosclerosis
• Thromboangitis obliterans( Buerger's disease)
• Raynaud's disease
• Trauma
• Ergot poisoning
Line of separation is formed between gangrenous and viable part.
20. Gross
• Affected part is dry, shrunken and dark black (foot of mummy)
• black due to liberation of Hb from haemolysed RBC's which is acted upon by H2S
produced by bacteria resulting in formation of black iron sulphide
• Line of separation- separation with falling off the gangrenous tissue
Microscopy
• Necrosis with smudging off tissue. Line of separation consists of inflammatory
granulation tissue.
21.
22. WET GANGRENE
• It occurs in moist tissues and organs such as mouth, bowel, lung, cervix, vulva,
etc
Examples:
• Diabetic foot
• Bed sores
Wet gangrene develops due to blockage of venous and less commonly arterial
Affected part is stuffed with blood- growth of putrefactive bacteria
No clear cut line of demarcation, may spread to peritoneal cavity causing
peritonitis.
23. Gross-
• Affected part is soft, swollen, putrid, rotten and dark.
Microscopy-
• Coagulative necrosis with stuffing of affected part with blood.
• No clear cut line of demarcation.
24.
25. GAS GANGRENE
• It is form of wet gangrene caused by gas forming clostridia. ( gram positive anaerobic
bacteria)•
Gross
• Affected tissue swollen, oedematous, painful and crepitant due to accumulation of gas
bubbles within the tissues
• Later tissue becomes dark black and foul smelling.
Microscopy
• Muscle fibres show coagulative necrosis with liquefaction, edema and leucocytic infiltrate
