Ans is 'd' i.e., Lung INFARCTION o An infarct is an area of ischemic necrosis by occlusion of either the aerial supply or venous drainage in a paicular tissue. Pathogenesis o Mostly it is caused by interrupted blood supply. o "Nearly 99% of all infarcts results from thrombotic or embolic events and almost all result. from aerial occlusion". o Other causes of interrupted aerial supply are local vasospasm, extrinsic compression of a vessel by tumor, twisting of vessel e.g., in testicular torsion, expansion of atheroma due to hemorrhage within the plaque. o Venous obstruction usually cause congesion, edema, infarction does not occur because bypass channels rapidly open after the thrombus, providing some outflow from the area, which inturn improves aerial inflow. Infarct cause by venous thrombosis is more likely in organs with a single venous outflow channel, such as in testis and ovary. Types of infarct o Infarcts are classified on the basis of their color. o Infarcts are classified into either Red (Haemorrhagic) or White or Pale (anaemic) infarcts, reflecting the amount of haemorrhage. Red infarcts (Haemorrhagic) : occur with : Venous occlusions (eg ovarian torsion); In loose tissues (such as lungs); In tissues with dual circulation (e.g. Lung & S. intestine) In tissues that were previously congested because of sluggish venous out flow. When flow is reestablilshed to a site of previous aerial occulusion and necrosis. White or Pale infarcts : occur with : Aerial occlusions, or In solid organs e.g. Hea, spleen, Liver, kidney and brain where the solidity of tissue limits the amount of haemorrhage that can seep into the area of ischaemic necrosis.