CELL DEATH Flashcards
What is the morphologic hallmark of cell death?
Loss of the nucleus via pyknosis, karyorrhexis, and karyolysis.
What are the two mechanisms of cell death?
Necrosis and apoptosis.
What is necrosis?
Death of large groups of cells followed by acute inflammation.
Is necrosis ever physiologic?
No, it is always due to an underlying pathologic process.
What is coagulative necrosis?
Necrotic tissue that remains firm; cell shape and organ structure are preserved but the nucleus disappears.
Which type of necrosis is characteristic of ischemic infarction?
Coagulative necrosis (except in the brain).
What is liquefactive necrosis?
Necrotic tissue that becomes liquefied due to enzymatic lysis of cells and proteins.
Which conditions are associated with liquefactive necrosis?
Brain infarction, abscess, pancreatitis.
What is gangrenous necrosis?
Coagulative necrosis that resembles mummified tissue (dry gangrene).
Where is gangrenous necrosis typically seen?
Lower limb and GI tract ischemia.
What happens if there is a superimposed infection on gangrenous necrosis?
Liquefactive necrosis ensues (wet gangrene).
What is caseous necrosis?
Soft and friable necrotic tissue with a ‘cottage cheese-like’ appearance.
Which conditions are associated with caseous necrosis?
Granulomatous inflammation due to tuberculosis or fungal infection.
What is fat necrosis?
Necrotic adipose tissue with chalky-white appearance due to calcium deposition.
Which conditions cause fat necrosis?
Trauma to fat (e.g., breast) and pancreatitis-mediated damage to peripancreatic fat.
What is fibrinoid necrosis?
Necrotic damage to blood vessel walls with fibrin deposition, appearing bright pink microscopically.
Which conditions are associated with fibrinoid necrosis?
Malignant hypertension and vasculitis.
What is apoptosis?
ATP-dependent, genetically programmed cell death of single cells or small groups of cells.
Give examples of apoptosis.
Endometrial shedding, removal of cells during embryogenesis, CD8+ T cell-mediated killing of virally infected cells.
What is the morphology of apoptotic cells?
Cell shrinkage, eosinophilic cytoplasm, nuclear condensation and fragmentation, apoptotic bodies removed by macrophages.
Which enzymes mediate apoptosis?
Caspases.
How do caspases promote apoptosis?
They activate proteases (breaking down the cytoskeleton) and endonucleases (breaking down DNA).
What are the pathways of caspase activation?
Intrinsic mitochondrial, extrinsic receptor-ligand, and cytotoxic CD8+ T cell-mediated pathways.
How is the intrinsic mitochondrial pathway activated?
Cellular injury, DNA damage, or decreased hormonal stimulation inactivates Bcl2, allowing cytochrome c to leak and activate caspases.
