0516 - ischaemia Flashcards
differentiate hypoxia and ischaemia
hypoxia is when there is a decrease in available oxygen to tissues.
ischaemia is the loss of blood supply to areas.
difference is hypoxia is only concerned with oxygen while ischaemia also affects other substrates, e.g. glucose.
Ischemia is result of decreased blood perfusion and all substrates are decreased. Hypoxia is deprivation of oxygen alone; it can arise therefore from anaemia or low environmental pO2.
what factors can contribute to how badly a cellular injury is?
where it is - some organs are more precious than others
environment - what’s already existing, previous damage
how quickly - slow narrowing v. embolism
mechanism of agent - intravenous versus swallowed
compare reversible and irreversible cell injury
removal of agent may result in full cell function again or while function may be altered cell still exists.
irreversible damage ends in necrosis and apoptosis.
what are some common effects of cellular injury?
ATP depletion
free radical production
loss of homeostasis
mitochondrial damage
what are some reversible celluarl changes in ischaemia
drop in mitochondrial function, leads to decrease in ATP
ATP enzymes are affected (transporters, signals, homeostasis disturbed)
decrease in protein synthesis
lipid deposition
contraction stops in heart cells
these effects are not visible under light microscope
what happens if oxygen is restored?
may actually do more harm than good. this is due to free radical production
what are some irreversible celluarl changes in ischaemia
cytoplasm will degrade due to lysosomes
mitochondria swells
cytoplasmic material detected in plasma
describe what necrosis looks like
cytoplasm more eosin - pink
nucleus more basophilic - purple
nucleus becomes shrunken
what is the process of apoptosis
programmed cell death
chromatin condensation
DNA fragmentation
What is ischaemia-reperfusion injury? Example?
Reintroduction of oxygen into tissue previously very low in tissue pO2. Free radical generation causes significant membrane damage in particular. One of best recognised examples is cardiac damage following re-perfusion of coronary artery after successful stenting or thrombolysis. Clinical effects seen include cardiac dysrhythmias and sudden death.
BP falls fast, patient resuscitated successfully. Next day, plasma ALT (liver cytosolic enzyme) found to be ↑↑. Explain why.
Very low BP associated with decreased liver perfusion (via both hepatic artery and portal vein). Successful resuscitation restores blood flow and oxygenation improves. This re-perfusion injury seen as damage and death of hepatocytes, ALT released into circulation and measured next day as still circulating in peripheral blood (plasma).
