Topics:
Animal Physiology, Animal Refresher
Initiating Factor of Extrinsic Clotting Pathway
Factor responsible for initiation of the extrinsic pathway of blood clotting is:
- Collagen
- Tissue factor (Tissue thromboplastin) — Correct Answer
- Factor X
- Calcium
Explanation:
Correct Answer: Tissue factor (Tissue thromboplastin)
The extrinsic pathway (also called the tissue factor pathway) is initiated by the release of Tissue Factor (Factor III / Tissue Thromboplastin) from damaged tissue at the site of injury.
Extrinsic vs. Intrinsic Pathway
| Feature | Extrinsic Pathway | Intrinsic Pathway |
|---|---|---|
| Initiating factor | Tissue Factor (Factor III) | Collagen (via Factor XII - Hageman factor) |
| Speed | Faster | Slower |
| Trigger | Tissue damage (external) | Contact with collagen (internal) |
Common Pathway
- Both pathways converge at activation of Factor X to Factor Xa.
- Factor Xa + Factor V → Prothrombinase complex → Prothrombin → Thrombin
- Thrombin → converts Fibrinogen → Fibrin (clot)
- Key enzyme in hemostasis: Thrombin
- Enzyme for clot lysis: Plasmin
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
