ischaemia and infarction Flashcards
What is ischaemia?
reduction in blood flow
What is infarction?
reduction in blood flow with subsequent death of cells
Which organs are very susceptible to infarction?
Those with an end arterial supply: intestines brain (middle cerebral artery) heart kidneys
Which organs have a dual arterial supply?
liver
lung
[brain (around circle of willis) but the arteries from the CoW are end arterial supplies]
Does an infarct cause inflammation?
yes
What is the general term for death of tissue within the living organism?
necrosis, infarction is specifically death from ischaemia
What is reperfusion injury?
When blood returns to an area that is ischaemic, it encounters tissue where the transport mechanisms have been disrupted, triggers oxygen-dependent free radical systems causing injury by apoptosis
What are the main stages of infarcts?
- inflammatory reaction at the edge
- dead myocytes removed by macrophages
- replacement by fibrous tissue forming scar
What is gangrene?
When mixed tissues die in bulk as whole areas have their blood supply cut off
What is disseminated intravascular coagulation?
thrombosis becomes activated without sufficient counterbalance and small thrombi form throughout the body.
Bleeding occurs at many sites, as coagulation factors are used up
Give an example of a watershed area
subendocardium
What increases the risk of infarction in a watershed area?
drop in BP e.g. following surgery, trauma or toxic shock from infection
What is a watershed area?
tissue at the interface between adjacent territories of two arteries
give examples of watershed areas
- splenic flexure of the colon (at the interface between the inferior and superior MA)
- cerebral hemispheres between the territories of the major cerebral arteries
- subendocardial myocardium
What factors can lead to ischaemia/infarction?
end arterial supply watershed area portal vasculature arterial stenosis high metabolic activity
