Pathway activated on contact with glass test tube by itself is termed ?
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 vitro'pathway 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.
Intrinsic pathway
Extrinsic pathway
Both the above
None of the above