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Pathology & Physiology (Subject) / PIPs (Lesson)

Necrosis, Oncosis and Apoptosis

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  • Def. Necrosis "Tissue that has died within an otherwise living organism"
  • Sorts of Necrosis 1. "Wet gangrene": discoloured, infected dead tissue, from which the infection can spread to other organs  2. "Dry gangrene": affects the limbs and results from a poor blood supply, little or no infection 
  • Oncosis - Cell death associated with ruptures of cell membranes --> release of digestive enzyms from lysosomes which hydrolyse cell components - always pathological - passive process  - inflammation occurs 
  • Apoptosis - "programmed cell death" - can be pathological or a part of normal physiology and growth  - active process which requires energy (ATP) - Membranes remain intact and no inflammation occurs  - the enzyme famiy "caspase" initiate the apoptosis by activation "executioner" caspades in a cascade system --> apoptotoc bodies present antigen "Phosphatidylserine" which is recognised by immune cells --> phagocytosis 
  • Ischaemia and infarction - Hypoxic tissue injury due to a restriction of blood supply is called Ischaemia --> leads to a shortage of oxygen  - Necrosis due to ischaemie is called infarction 
  • Pathopathology of hypoxic cell injury Lack of oxygen --> decreased oxidative phosphorylation --> Decreased ATP --> membrane damage --> Rupture of lysosymes and ER 
  • Mitochondrial damage (Effects and results) Effects: less ATP and more ROS (reactive oxygen species) Results: loss of energy supplyand damage to lipids, proteins, DNA --> Necrosis due to oncosis
  • Entry of Ca2+ (Effects and results) Effects: Increase in mitochondrialpermeability and activation of multiple cellular enzymes (phospholipase, protease, ATPase, endonuclease) Results: less ATP and destruction of cell membranes (loss of phospholipids and proteins) and nuclear damage
  • Membrane damage (effects and results) Effects: Plasma membrane and lysosomal membrane damaged Results: Loss of cellular components and enzymatic digestion of cellular components
  • Protein misfiling, DNA damage (results and effects) Effects: Activation of pro-apoptotic proteins Results: Apoptosis 
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  • Autolysis - death of cells due to release of digestive enzymes from inside the cell (lysosomes) - accors after death of the whole organism or after removal of a part (e.g. organ) - no form of necrosis, because necrotic changes inly occur in living organisms

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