NECROSIS
Definition:- Necrosis is defined as a localised area of death of tissue followed later by degradation of tissue by hydrolytic enzymes liberated from dead cells; it is invariably accompanied by inflammatory reaction.
Based on etiology and morphologic appearance, there are 5 types of necrosis: coagulative, liquefaction (colliquative), caseous, fat, and fibrinoid necrosis.
1. COAGULATIVE NECROSIS:- This is the most common type of necrosis caused by irreversible focal injury, mostly from sudden cessation of blood flow.
2. LIQUEFACTION (COLLIQUATIVE) NECROSIS:- Lique- faction or colliquative necrosis also occurs commonly due to ischaemicinjury and bacterial or fungal infections but hydrolytic enzymes in tissue degradation have a dominant role in causing semi-fluid material.
The common examples are infarct brain and abscess cavity.
3. CASEOUS NECROSIS:- Caseous (caseous= cheese-like) necrosis is found in the centre of foci of tuberculous infections. It combines features of both coagulative and liquefactive necrosis.
4. FAT NECROSIS:- Fat necrosis is a special form of cell death occurring at mainly fat-rich anatomic locations in the body.
example mesenteric fat necrosis due to acute pancreatitis.
5. Fibrinoid necrosis:- is characteri- sed by deposition of fibrin-like material which has the staining properties of fibrin such as phosphotungistic acid haematoxylin (PTAH) stain.
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