Morphology: Reversible Injury (EM)

  1. Membrane bleb
  2. Mitochondrial swelling
  3. Swelling of ER and detachment of the ribosomes
  4. Nuclear changes


Morphology: Reversible Injury (LM)

  1. Cell swelling: hydropic, vacuoles
  2. Fatty change


Morphology: Irreversible Injury (LM)

Nuclear changes

  1. Karyolysis: pale nuclei
  2. Pyknosis: nuclear shrinkage and basophilia
  3. Karyorrhexis: fragmentation of pyknotic nuclei

Patterns of Necrosis:

  1. Coagulative Necrosis: common following ischemia. There is complete denaturation of proteins including the catabolic enzymes. Morphology: preservation of the basic structure of the tissue.
  2. Gangrenous Necrosis: occurs in ischemic limb. When it is superimposed by infection, it is called “wet gangrene”
  3. Liquefactive Necrosis: common following infection by bacteria or fungi due to the enzymatic action of neutrophils. Morphology: digestion of all the cell component resulting in amorphous cellular debris. Brain infarction usually result in liquefactive necrosis.
  4. Caseous Necrosis: is a special form of necrosis that happen with TB. Morphology: granuloma with central necrosis. The necrosis is grossly white, cheesy material.
  5. Fat Necrosis: happens in fat destruction, common in pancreatitis after the release of lipase from pancreatic acini. The free fatty acids combine with Ca++ and result in “saponification”