Necrosis

• Def.:

  death of group of cells within living body resulting to inflammatory response and repaired by fibrosis. Dystrophic calcification may occur
• Mechanism

  • Severe or prolonged moderate injury
  • damage of cell membrane
  • release lysosomal enzymes
  • destruction of cell
  • Leakage of cell constitutes
  • inflammation
  • Necrotic area is removed by macrophages
  • healing by fibrosis or destrophic calcification
  • Two processes underling morphological changes:
  • Denaturation of proteins
  • enzymatic digestion
• Nuclear changes

  1. Pyknosis: nuclear shrink & stains darkly (increased basophilia)
  2. karyorrhexis: destructive nuclear fragmentation
  3. karyolysis: faint nuclear basophilia (fading)
  4. nucleus disappears completely
• Cytoplasmic changes

  the cells appear homogenous, structureless, and pink

  • increased eosinophilia (pink staining)
  • (++) denatured cytoplasmic proteins
  • loss of the basophilia "the ribonucleic acid (RNA) in the cytoplasm"
  • homogeneous appearance
• Architectural changes (cell membrane)

  1. structureless loss of cell border definition
  2. autolysis by lysosomal enzymes
  3. protein denaturation (coagulation) may proceed lysis so necrotic cells preserve architectural outlines