Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

The intrinsic pathway of the coagulation cascade starts with the activation of certain factors that are vital for initiating the clotting process. The correct choice includes Factor XII, Fitzgerald factor (also known as Factor XIIa), and Fletcher factor, all of which play crucial roles in the initial stages of this pathway.

Factor XII is activated upon contact with negatively charged surfaces or trauma to the vascular system, triggering the intrinsic pathway. Once activated, it converts prekallikrein to kallikrein, which in turn activates more Factor XII molecules in a positive feedback loop. Fitzgerald factor is essentially synonymous with prekallikrein and serves as a substrate in this activation process, while Fletcher factor refers to high-molecular-weight kininogen, which is also involved in the activation of Factor XII and plays a role in promoting coagulation.

Understanding the roles of these factors provides insight into how the intrinsic pathway of coagulation is initiated, which is critical for forming a stable clot in response to vascular injury.