Why is intrinsic pathway not activated in vivo?

[sameeralord]

Hello everyone,

The book says invivo extrinsic pathway is the one that gets activated, but intrinsic pathway is activated by surface collagen, so it must be activated as well. Both must be activated right, also if a person is deficient of intrinsic pathway clotting factors, would they have no problems with clotting because extrinsic pathway is the major one involved. Thanks :smile:

[SW VandeCarr]

Hello everyone,

The book says invivo extrinsic pathway is the one that gets activated, but intrinsic pathway is activated by surface collagen, so it must be activated as well. Both must be activated right, also if a person is deficient of intrinsic pathway clotting factors, would they have no problems with clotting because extrinsic pathway is the major one involved. Thanks :smile:

Yes. The extrinsic (tissue factor III+VII) is the major pathway and is activated by trauma. The intrinsic pathway (Factor XII) is surface activated and is less important. It need not be activated for an adequate clotting cascade.