Necrosis

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Necrosis

  1. 1. NECROSIS 1
  2. 2. OBJECTIVES• Highlight the basic concepts and principles of necrosis (cell death)• Differentiate between different types of necrosis 2
  3. 3. CONTENTS4.1 Definition of necrosis4.2 Different types of necrosis4.3 Different types of necrosis base on pathologic changes 3
  4. 4. 4.1 Definition Of Necrosis• Necrosis; defined as focal death along with degradation of tissue by hydrolitic enzymes liberated by cells. It’s invariably accompanied by inflammatory reaction.• Causes; 1. Loss of blood supply - caused by blockage of a vessel by a blood clot which produces immediate local anoxia. 2. Bacterial toxins – inflammation is produced & if it’s strong the result is necrosis. 3. Physical irritants – excessive heat, excessive cold, trauma & radiation. 4. Chemical irritants – strong acid. 4
  5. 5. 4.2 Types Of Necrosis• Morphologically, 5 types of necrosis are identified: i) Coagulative necrosis ii) Liquefaction (Colliquative) necrosis iii) Caseous necrosis iv) Fat necrosis v) Fibrinoid necrosis• Gangrene is a form of necrosis of tissue with superadded putrefaction; gangrene necrosis 5
  6. 6. i) Coagulative necrosis Most common type of necrosis caused by irreversible focal injury (mostly because ischaemia). Less often bacterial & chemical agents. The organs commonly affected are HEART, KIDNEY & SPLEEN. 6
  7. 7. Coagulative necrosis – Renal infarction 7
  8. 8. Coagulative necrosis – Spleenic infarction 8
  9. 9. ii) Liquefaction (Colliquative) necrosis Occurs commonly due to ischaemic injury & bacterial or fungal infections. Occurs due to degradation of tissue by the action of powerful hydrolytic enzymes. Examples are INFARCT BRAIN (stroke) & ABSCESS CAVITY. 9
  10. 10. Liquifactive necrosis - Stroke 10
  11. 11. Liquifactive necrosis – Liver abscess 11
  12. 12. iii) Caseous necrosis Found in the centre of foci of tuberculosis infections. It combines features of both coagulative & liquefactive necrosis. 12
  13. 13. Caseous necrosis -Tuberculosis 13
  14. 14. Caseous necrosis -Tuberculosis 14
  15. 15. iv) Fat necrosis Special form of cell death occurring at two anatomically different locations but morphologically similar lesions. These are ACUTE PANCREATIC NECROSIS & TRAUMATIC FAT NECROSIS (breast). In the case of pancreas, there is liberation of pancreatic lipase from injured or inflamed tissue that results in necrosis of the pancreas. Fat necrosis in either of the two instances results in hydrolysis of neutral fat present in adipose cells into glycerol & free fatty acid. 15
  16. 16. v) Fibrinoid necrosis Characterized by deposition of fibrin-like material which has the staining properties of fibrin. It’s encountered in various examples of immunologic tissues injury, arterioles in hypertension, peptic ulcer etc.vi) Gangrene necrosis The type of necrosis is usually coagulative due to ischaemia. Is characterized by primarily inflammation provoked by virulent bacteria. 3 types; dry, wet & gas gangrene. 16
  17. 17. 4.3 Types Of Necrosis Base On Pathologic Changesi) Coagulative necrosis Grossly: foci of coagulative necrosis in the early stage are PALE, FIRM & SLIGHTLY SWOLLEN. : with progression, they become more YELLOWISH, SOFTER & SHRUNKEN. Micro: the pattern of microscopic change results from 2 processes which are DENATURATION OF PROTEINS & ENZYMATIC DIGESTION OF THE CELL. 17
  18. 18. ii) Liquefaction (Colliquative) necrosis Grossly: the affected area is soft with liquefied centre containing necrotic debris. : later, a cyst wall is formed. Micro: the cystic space contains necrotic cell debris & macrophages filled with phagocytosed material. : the cyst wall is formed by proliferating cappilaries, inflammatory cells & gliosis (proliferating glial cells) in the case of brain & proliferating fibroblasts in the case of abscess cavity. 18
  19. 19. iii) Caseous necrosis Grossly: resemble dry cheese and are soft, granular & yellowish. Micro: the necrosed foci are structureless, eosinophilic & contain granular debris.iv) Fat necrosis Grossly: appears as yellowish-white & firm deposits. : formation of calcium soaps imparts the necrosed foci firmer & chalky white appearance. Micro: necrosed fat cells have cloudy appearance & are surrounded by an inflammatory reaction. 19
  20. 20. v) Fibrinoid necrosis Grossly: is identified by brightly eosinophilic, hyaline-like deposition in the vessel wall or on the luminar surface of peptic ulcer. : local haemorrhages may occur due to rupture of these blood vessels.vi) Dry gangrene Macro: the affected part is dry, shrunken & dark black, resembling the foot : it’s black due to liberation of haemoglobin from haemolysed red blood cells. Histo: the separation consists of inflammatory granulation tissue. 20
  21. 21. vii) Wet gangrene Macro; the affected part is soft, swollen, putrid, rotten & dark. : the example is gangrene of bowel. Histo: there is ulceration of the mucosa & intense inflammatory infiltration.viii) Gas gangrene Grossly: the affected area is swollen, edematous, painful & crepitant due to accumulation of gas bubbles within the tissues. : the affected tissue becomes dark black & foul smelling. Micro: at the periphery, a zone of leucocytic infiltration, edema & congestion are found. 21
  22. 22. THANK YOU 22

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