Tissue Factor Extrinsic — FRCA Primary MCQ
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Correct answer: E — Extrinsic pathway
Tissue factor (thromboplastin / factor III) is released from damaged subendothelial tissue and initiates the extrinsic pathway by forming a complex with factor VIIa. This complex activates factor X (the start of the common pathway). The extrinsic pathway is monitored by PT/INR. The intrinsic pathway (contact activation) is monitored by aPTT.
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist