alleryStart learning →What is the first step in hemostasis?
AFormation of the platelet plug
BVascular spasm of the vessel wall
CConversion of fibrinogen to fibrin
DActivation of the common pathway
Answer & Solution
Correct answer: B. Vascular spasm of the vessel wall
1. Hemostasis runs in three steps: vascular spasm, formation of a platelet plug, then coagulation.
2. Vascular spasm comes first, narrowing the vessel and cutting the rate of blood loss immediately.
3. The platelet plug follows and buys time while the durable repair is built.
4. Fibrin formation belongs to coagulation, the last of the three, so options built on it are out of order.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_
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