How is the intrinsic pathway of coagulation activated?

The intrinsic pathway of coagulation is activated primarily by damage to blood vessels. This pathway is part of the body's natural response to injury and involves a series of chemical reactions that take place when blood vessels are compromised. When blood vessels are damaged, collagen and other substances that are normally not exposed to flowing blood become available, initiating the activation of clotting factors in the intrinsic pathway.

This pathway is characterized by the involvement of several factors, including factor XII, which can be activated upon contact with exposed collagen. The intrinsic pathway typically operates in conjunction with the extrinsic pathway to form a stable clot; however, its initiation is closely tied to vascular damage.

Other options involve different mechanisms of coagulation activation. External trauma generally initiates the extrinsic pathway more directly, while platelet aggregation is a later stage in the clotting process influenced by both pathways. The presence of thrombin signals the process of clot formation but does not initiate the intrinsic pathway itself.