Question:easy
The extrinsic system of coagulation is activated by?
The extrinsic system of coagulation is activated by?
Show Hint
The pathway from outside the vessel begins with tissue factor.
Updated On: Jun 24, 2026
- Factor XI
- Factor X
- Factor XII
- Factor III
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Coagulation runs along two arms. The intrinsic arm starts inside the vessel from contact activation (Factor XII), and the extrinsic arm starts from outside the vessel after tissue injury.
Step 2: Injured tissue releases tissue factor, which is named Factor III or tissue thromboplastin. This is the spark for the extrinsic pathway.
Step 3: Tissue factor joins Factor VII and calcium ions to switch on Factor X. From Factor X onward both arms share the common pathway, so Factor X is convergence rather than the extrinsic starter, and Factors XI and XII sit in the intrinsic arm.
Step 4: Hence the molecule that activates the extrinsic system is Factor III.
\[\boxed{\text{Factor III (tissue factor)}}\]
Step 2: Injured tissue releases tissue factor, which is named Factor III or tissue thromboplastin. This is the spark for the extrinsic pathway.
Step 3: Tissue factor joins Factor VII and calcium ions to switch on Factor X. From Factor X onward both arms share the common pathway, so Factor X is convergence rather than the extrinsic starter, and Factors XI and XII sit in the intrinsic arm.
Step 4: Hence the molecule that activates the extrinsic system is Factor III.
\[\boxed{\text{Factor III (tissue factor)}}\]
Was this answer helpful?
0
