Necrosis and apoptosis

Objectives Define necrosis and apoptosis List the different types of necrosis, examples of each and its features List the different conditions associated with apoptosis, its morphology and its mechanism Know the difference between apoptosis and necrosis

Objectives Define necrosis and apoptosis List the different types of necrosis, examples of each and its features List the different conditions associated with apoptosis, its morphology and its mechanism Know the difference between apoptosis and necrosis

Cell Death Death of cells occurs in two ways: Necrosis--(irreversible injury) changes produced by enzymatic digestion of dead cellular elements Apoptosis--vital process that helps eliminate unwanted cells--an internally programmed series of events effected by dedicated gene products

Objectives Define necrosis and apoptosis List the different types of necrosis, examples of each and its features List the different conditions associated with apoptosis, its morphology and its mechanism Know the difference between apoptosis and necrosis

Morphology of necrosis : Cellular swelling or rupture Denaturation  and coagulation of cytoplasmic proteins Breakdown of cell organelles Breakdown of nuclear DNA

Patterns of Necrosis In Tissues or Organs As a result of cell death the tissues or organs display one of these six macroscopic changes: Coagulative necrosis Liquifactive necrosis Caseous necrosis Fat necrosis Gangrenous necrosis Fibrinoid necrosis

Patterns of Necrosis In Tissues or Organs Coagulative necrosis: the outline of the dead cells are maintained and the tissue is somewhat firm. Example: myocardial infarction  Liquefactive necrosis: the dead cells undergo disintegration and affected tissue is liquefied. Example: cerebral infarction.

Patterns of Necrosis In Tissues or Organs 3. Caseous necrosis: a form of coagulative necrosis (cheese-like). Example: tuberculosis lesions. 4. Fat necrosis: enzymatic digestion of fat. Example: necrosis of fat by pancreatic enzymes. 5. Gangrenous necrosis: Necrosis (secondary to ischemia) usually with superimposed infection. Example: necrosis of distal limbs, usually foot and toes in diabetes. 6. Fibrinoid necrosis: typically seen in vasculitis and glomerular autoimmune diseases

Changes in the cytoplasm and the nucleus Coagulative Necrosis   Changes in the cytoplasm and the nucleus   Karyorrhexis Karyolysis  Pyknosis

Necrosis of the liver induced by herpesvirus. Herpesvirus invades liver cell nuclei producing nuclear ('ground glass') mildly basophilic inclusions.

Acute renal tubular necrosis (ischemia) : increased eosinophilia and pyknosis in necrotic cells Normal Necrotic

Ischemic neuronal injury:acidophilic cytoplasm & nuclear pyknosis

… a mess - so many cells have died - the tissue is not recognizable … a mess - so many cells have died - the tissue is not recognizable. Nuclei have become pyknotic (shrunken and dark), undergone karorrhexis (fragmentation) and karyolysis(dissolution) Necrotic myocardium

Removal of the dead tissue leaves behind a scar Coagulative necrosis Kidney: ischemia and infarction (loss of blood supply and resultant tissue anoxia). Removal of the dead tissue leaves behind a scar

Infarcts (vascular distribution) are wedge-shaped Coagulative necrosis: is due to loss of blood supply Infarcts (vascular distribution) are wedge-shaped with a base on the organ capsule. Spleen

Depending on circumstances: necrotic tissue may be walled off by scar tissue, totally converted to scar tissue, get destroyed (producing a cavity or cyst), get infected (producing an abscess or "wet gangrene"), or calcify. If the supporting tissue framework does not die, and the dead cells are of a type capable of regeneration, you may have complete healing. Remember: True coagulation necrosis involves groups of cells, and is almost always accompanied, by acute inflammation (infiltrate)