Cell injuries 3

• Types of cell death

  • Necrosis
  • Apoptosis
• Necrosis


  Local death of a group of cells within the living body
• Apoptosis


  Genetically controlled programmed single cell death
• Morphological features of necrosis (gross)

  • The necrotic area is well-defined, swollen, opaque, pale yellow or pale red and surrounded by a red zone of inflammatory hyperemia
• Morphological features of necrosis (microscopic)

  • Cell membrane disappear & the cells become indistinct from each other
  • Cytoplasm: swollen & coagulated, appears homogenous and deeply eosinophilic
  • Nucleus: Pyknosis, Karyorrhexis, Karyolysis
• Types of necrosis


  • Coagulation necrosis
  • Liquefactive necrosis
  • Caseation necrosis
  • Fat necrosis
  • Fibrinoid necrosis
• Coagulative necrosis


  Denaturation and coagulation of structural and enzymatic proteins, preserving cell outlines and tissue architecture
• Coagulative necrosis


  • Myocardial infarction due to coronary artery occlusion
• Liquefactive necrosis


  • Ischemic necrosis of brain (infarction)
  • Pyogenic abscess
• Caseation necrosis


  Combination of coagulative and liquefaction necrosis, tissue is firm and without cellular details or tissue outline
• Caseation necrosis


  • Tuberculosis
• Fat necrosis


  Necrosis of fat cells by either trauma to fatty tissue or by the action of lipase enzyme
• Fat necrosis


  • Traumatic fat necrosis of the breast
  • Enzymatic fat necrosis of the pancreas and omentum in case of acute hemorrhagic pancreatitis
• Fibrinoid necrosis


  Death of cells in the inner layer of small blood vessels, can lead to bleeding and internal damage
• Causes of fibrinoid necrosis

  • Malignant hypertension
  • Autoimmune diseases
  • Subacute bacterial endocarditis
  • Vasculitis
• Morphological appearance of apoptotic cells

  • Cell shrinkage
  • Cytoplasm becomes deeply eosinophilic
  • Nucleus becomes pyknotic then fragments
  • Cell membrane does not rupture
  • Formation of cytoplasmic buds
  • Each nuclear fragment goes with a cytoplasmic bud and breaking off to form apoptotic bodies
  • Phagocytosis of apoptotic bodies by adjacent cells or macrophages
  • Lack of inflammatory response
• Physiologic examples of apoptosis

  • Embryogenesis
  • Hormone-dependent involution in adults
  • Removal of self reacting T-lymphocytes in Thymus
• Pathologic examples of apoptosis

  • Councilman bodies = apoptotic hepatocytes in viral hepatitis
  • Tumor cell death
  • Neurons that are lost in Alzheimer's disease
  • HIV-positive T-lymphocytes die by apoptosis