Medical Laboratory Scientist (MLS) ASCP Practice Exam

The intrinsic pathway of coagulation is a series of complex reactions initiated by the activation of Factor XII upon contact with negatively charged surfaces, which leads to a cascade resulting in clot formation. Factors included in the intrinsic pathway primarily consist of Factor XII, Factor XI, Factor IX, and Factor VIII.

Factor VII is not part of the intrinsic pathway; instead, it is associated with the extrinsic pathway. The extrinsic pathway is triggered by tissue factor (TF) released from damaged tissues and works in conjunction with Factor VII, which becomes activated to Factor VIIa and initiates the coagulation process in response to vascular injury.

The presence of Factor IX and the earlier factors, such as Factor XII and Factor XI, confirms their role in the intrinsic pathway, highlighting the distinction of Factor VII’s involvement exclusively with the extrinsic pathway. Thus, identifying Factor VII as an outlier in the context of the intrinsic pathway illustrates an understanding of the separate mechanisms of hemostasis.