Multiple choice

The coagulation of blood in vessels is prevented during normal conditions by

  1. heparin

  2. plasminogin

  3. calcium

  4. prothrombin

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Heparin, produced by mast cells and basophils, acts as a natural anticoagulant by enhancing antithrombin III activity, which inhibits thrombin and factor Xa. This prevents inappropriate clotting in intact blood vessels during normal circulation.