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Created page with " * Ischaemia is the failure or reduction of arterial blood supply to an organ or tissue. ===Causes=== * Arteriospasm ** Arterial trauma ** Ergotism ** Other drug effects * Co..."
* Ischaemia is the failure or reduction of arterial blood supply to an organ or tissue.
===Causes===
* Arteriospasm
** Arterial trauma
** Ergotism
** Other drug effects
* Compression of arteries/ arterioles
** Ligatures
** Tourniquets
* Thromboembolism
** Vascular impaction by embolic fragments
===Sequelae===
* Several factors determine the extent and consequences of arterial obstruction.
*# Degree of occlusion
*#* May be partial or complete.
*# Rapidity of occlusion
*#* May be sudden or gradual.
*# Presence and extent of a collateral circulation, such as
*#* Anastomoses
*#* Whether end areterioles are functional or actual.
*#* Efficient alternative arterial supplies.
*# Vulnerability of tissues/ cells to ischemia.
*#* For example, their oxygen dependency and metabolic rate.
*#** E.g. neurones and cardiac myocytes are much more susceptible than fibrous tissue.
* There are two possible scenarios in ischeamia, each with their own sequelae.
*# '''Complete, sudden failure of blood supply'''
*#* Unless there is a good alternative collateral supply, this results in necrosis of tissue.
*#** Collateral supplies may be inadequate to compensate if the blockage is severe.
*#* This focal type of lesion is known as [[Ischaemia and Infarction - Pathology#Infarction|'''infarction''']].
*# '''Incomplete, gradual failure of blood supply'''
*#* Results in “accommodation”.
*#** Manifests as atrophy, sometimes with fibrosis, following cellular hypoxia.
*#*** Minimal fibrosis occurs if collateral/ alternative supplies are good.
[[Category:Circulatory Disorders - Pathology]]