Lecture 11: Cell injury and necrosis Flashcards
(13 cards)
What are the two types of cell death?
Necrosis: Accidental cell death.
Apoptosis: regulated cell death that eliminates unwanted and unrepairable cells with minimal host inflammatory response. Requires energy and leaves cell intact.
What is ischaemia?
Hypoxia induced by reduced blood flow, most commonly due to mechanical arterial obstruction. Can lead to death in 20-30 min.
What is an infarction?
Death of tissue due to loss of blood supply, most often as a result of arterial occlusion.
True or false? All cell injury leads to necrosis.
False. Sometimes injury is sublethal and can be reversed.
What is the key step in necrosis?
Depletion of mitochondrial ATP production. Death can occur before we see it.
At what point is a cell irreversibly injured?
When cell membranes break down. This is due to the breakdown of ATPases, therefore not allowing for production of more ATP. Dissolution of many membranes occur, and proteosomes and enzymes are released.
What is reperfusion injury?
It is when O2 is reintroduced into the system. This results in Oxygen free radicals that produce various oxygen species such as hydrogen peroxide, O2 superoxide and hydroxyl free radicals.
Ultimately causes DNA damage, protein modification, lipid peroxidation.
What types of necrosis are there?
Coagulative (NOT brain, but maybe kidney), liquefactive (brain), caesous (lung).
Briefly describe coagulative necrosis.
It occurs when enzymatic dissolution of tissue is slow. Nuclear changes include pyknosis and karyorrhexis, which is nuclear shrinkage and fragmentation.
Because of nucleus death, there is no longer protein production, so cytoplasm is extremely eosinophilic.
Briefly describe liquefactive necrosis.
Digestion of dead cells resulting in liquid mess. Inflammation due to cerebral infarction is mild.
Briefly describe caeseous necrosis.
Typical of tuberculosis, and gives off a cheesy appearance. Histology defines it as amorphous (no clearly defined shape) granular debris.
It occurs when tissue dissolution by enzymes is more advanced than in coagulative necrosis, but not yet enough to liquefy it.
What two pathways of apoptosis are there?
Intrinsic - via mitochondria. Caused by growth factor withdrawal, DNA damage, protein misfolding whereby abnormal proteins accumulate in ER due to mutation.
Extrinsic - via death receptor. Caused by TNF receptor binding.
What are the 4 steps of apoptosis?
Signalling, execution, degradation, phagocytosis. Results in fragmented (not swollen like necrosis) body, and remains functionally intact.
