Common Coagulation Pathway — MFDS Part 1 MCQ

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HardPhysiologyCommon Coagulation PathwayMFDS Part 1

In the contemporary model of coagulation, which zymogen is activated both by the tissue factor–factor VIIa complex during initiation and by the factor IXa–factor VIIIa complex during amplification, after which its activated form combines with factor Va to convert prothrombin to thrombin?

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Correct answer: E — Factor X

Factor X is the correct answer. Tissue factor bound to factor VIIa forms extrinsic tenase, which activates factor X during coagulation initiation. Factor IXa with its cofactor factor VIIIa forms intrinsic tenase, which activates factor X more efficiently during amplification. Factor Xa then combines with factor Va to form prothrombinase, converting prothrombin to thrombin. Factor VII is principally part of the tissue-factor pathway. Factors VIII and IX form the intrinsic tenase complex rather than being its factor X substrate. Factor XII initiates contact activation in the classical intrinsic pathway and is not the convergence factor. Thus, factor X links initiation and amplification to the common thrombin-generating pathway.

Reference: Park S, Park JK. Back to basics: the coagulation pathway. Blood Research. 2024;59(1):35. Abstract and Figure 1. https://pubmed.ncbi.nlm.nih.gov/39466528/