<prompt> Pathway activated on contact with glass test tube by itself is termed ?Intrinsic pathwayExtrinsic pathwayBoth the aboveNone of the above  <response>: Ans. is a i.e., Intrinsic pathway Contact with negatively charged surfaces activates the Intrinsic pathway of coagulation not the Extrinsic pathway, Intrinsic pathway is also referred to as contact pathway and factor XII is also known as contact factor for its role in the initiation of coagulation on contact with negatively charged surfaces. Activation of coagulation pathway Intrinsic and extrinsic pathways are activated by different mechanisms :? 1 Intrinsic pathway The intrinsic pathway is largely an in vitropathway of coagulation. However, it may be activated in vivo also. i In vitro activation :- Intrinsic pathway may be activated in vitro upon interaction of factor XII Hageman factor or contact factor with negatively charged surface such as glass, kaolin, dextran sulphate, ellagic acid, celite, or bismuth subgallate and interaction with hydrophobic surfaces. ii In vivo activation :- in vivo activation occurs as a result of contact activation of factor XII from subendothelial collagen and other components platelets following endothelial injury to blood vessels. As intrinsic pathway is largely an in vitro pathway, it is impoant for coagulation testing. 2 Extrinsic pathway The extrinsic pathway is largely an in vivo pathway and accounts for majority of in vivo coagulation. It may also be activated in vitro also. i In vivo activation :- in vivo activation occurs by the expression of tissue factor at the sites of tissue injury. In vitro activation :- in vitro activation occurs by exposure of blood to thromboplastin reagents tissue factor derived from tissues. 