alleryStart learning →What normally triggers the extrinsic coagulation pathway?
AContact with a glass test tube
BSlow blood flow in the leg veins
CTrauma to the surrounding tissues
DA fall in the plasma calcium level
Answer & Solution
Correct answer: C. Trauma to the surrounding tissues
1. The extrinsic pathway is named for factors that come from outside the bloodstream.
2. It begins when damage occurs to the surrounding tissues, as in a traumatic injury.
3. Damaged extravascular cells then release factor III, tissue thromboplastin, on contact with plasma.
4. Contact with a glass test tube activates factor XII and therefore starts the intrinsic pathway instead.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_
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