Hi guys, I know this is a simple question. But when an artery is blocked it is easier to understand because, less oxygen goes to tissue so, necrosis of tissue. But when a vein is blocked, only the draining is affected, the arteries are still able to supply oxygen, but why does necrosis still occur. I'm assuming it is because when a vein is blocked, it leads to congestion, increased back pressure, which makes it difficult for arterial blood to come and perfuse tissue. Just asked to clarify (I know this is probably a pretty obvious stupid question, but I like to get it clarified). Thanks While we are at it, if you know something about this, please tell me Does the pathogenesis of cerebral venous infarction differ considerably from the pathogenesis of cerebral arterial ischemic infarction. Why does a haemorrhagic infarct occur in cerbral venous infarction.