Irreversible cell i njury

irreversible cell injury and its phenomenon

1. IRREVERSIBLE CELL INJURY -By Abhaya Pratap

2. INTRODUCTION “All organ injuries start with structural or molecular alterations in cells” concept began by Virchow in 1800's •modern study of disease attempts to understand how cells react to injury, often at the subcellular or molecular level, and how this is manifested in the whole animal.

3. Classes of Cell Injury Irreversible --> cell death. Types: Necrosis : pathological ( dissolution of dead cells by its own digestive enzymes ) Apoptosis: PROGRAMMED cell death Reversible If stressor removed, and If cell damage mild: cells survive

4. PROBABLE CAUSES The first is the inability to reverse  mitochondrial dysfunction  (lack of  oxidative phosphorylation  and ATP generation ) even after resolution of the original injury. The second is the development of profound disturbances in membrane function.

5. NECROSIS

6. NECROSIS DEFINITION : Death of  a group  of  contiguous cells  within a living tissue  or organ Affect  both nucleus and cytoplasm Unregulated cell death with inflammation

7. Morphological changes DURING NECROSIS Cytoplasmic Nuclear Cytoplasmic changes  : Cytoplasmic eosinophilia due to loss of normal basophilia & increased binding of eosin to denaturated proteins (Granular or homogenous glassy)  Nuclear changes: Pyknosis : shrinkage-increased staining with haematoxylin Karyorrhexis : fragmentation Karyolysis : total disappearance

8. TYPES: NECROSIS Coagulative Liquefactive Caseation Fat Necrosis Fibrinoid Necrosis

9. COAGULATIVE NECROSIS In: infarcts of kidney, heart, spleen Gross: pale , yellow, opaque, firm Mic.: All cellular details are lost but general architecture of the tissue is preserved Surrounding tissue----acute inflammation Ex: Infarction - heart  Infarction - kidney           

10. LIQUEFACTIVE NECROSIS In: centers of pyogenic abscess amoebiasis infarcts of C.N.S. Necrotic tissue---completely liquified ---turbid fluid----absorbed----space Ex: Brain - infarction  Amoebiasis ---liver 

11. CASEATION NECROSIS In: Tuberculosis Necrotic tissue is partially liquefied---cheesy material ( caseation ) Mic : Both cellular details & general architecture of dead tissue are lost--- structureless eosinophilic material

12. FAT NECROSIS Traumatic : in female breast Enzymatic : in acute hemorrhagic pancreatitis Gross: opaque & white fat cells appear cloudy, surrounded by chronic inflammatory cells, histiocytes , foreign body giant cells          

13. Fibrinoid Necrosis Fibrinoid necrosis  is a form of  necrosis , or tissue death, in which there is accumulation of amorphous, basic, proteinaceous material in the tissue matrix with a staining pattern reminiscent of fibrin.        

14. APOPTOSIS

15. APOPTOSIS   (programmed   cell  death)  Definition: death of individual cells surrounded by viable cells when a  cell   dies through activation of an internally suicide program It is an active process—energy dependent Does not elicit inflammatory response May be physiologic or pathologic

16. APOPTOSIS CAUSES PHYSIOLOGIC During embryogenesis e.g. removal of interdigital webs during embryonic development of toes and fingers Hormone-dependent e.g. endometrial  cell loss in menstruation PATHOLOGIC Irradiated tissues Cell  death induced by cytotoxic T-lymphocytes Viral infections e.g. viral hepatitis Cell  death in tumours

17. Differences between necrosis and apoptosis Necrosis Death of groups of cells A passive process—not energy-dependent Elicits inflammatory response Always pathologic Apoptosis Death of individual cells Active process—energy-dependent Does not elicit inflammatory response May be pathologic or physiologic

18. Thank You