What is vascular spasm?

• A. Platelets adhere to damaged site to form a plug.
• B. Clotting factors convert fibrinogen to fibrin.
• C. Endothelial cells proliferate to close wound.
• D. Smooth muscle of injured vessel contracts to reduce blood flow and blood loss.

Answer: (D)

Vascular spasm is the immediate narrowing of a damaged blood vessel caused by contraction of its smooth muscle, which serves to reduce blood flow and limit blood loss.

This rapid vasoconstriction helps stabilize the injury window while the body sets up longer-lasting hemostatic plug and clot formation. The best description matches the idea that the smooth muscle of the injured vessel contracts to constrict the lumen and minimize bleeding.

Platelets adhering to the damaged site describes platelet plug formation, a later step in hemostasis, not the initial vasoconstriction. Clotting factors converting fibrinogen to fibrin refers to the coagulation cascade that reinforces the plug with a fibrin clot. Endothelial cells proliferating to close the wound is part of healing and remodeling, not the immediate vascular constriction.