Question

what can help prevent clots from forming in undamaged blood vessels?select all that apply.
a heparin from basophils and mast cells
b smooth endothelium of blood vessel walls
c prothrombin activator
d platelets adhering to collagen fibers

Explanation:

• Option A: Heparin is an anticoagulant. Basophils and mast cells secrete heparin which can prevent clotting in undamaged blood vessels by inhibiting the clotting cascade.
• Option B: The smooth endothelium of blood vessel walls prevents platelet adhesion and the activation of the clotting cascade. If the endothelium were rough, platelets and clotting factors could be activated more easily.
• Option C: Prothrombin activator is involved in the clotting process. It converts prothrombin to thrombin (a key enzyme in clot formation), so it does not prevent clotting.
• Option D: Platelets adhering to collagen fibers (which are exposed when a blood vessel is damaged) is part of the clot - forming process (platelet plug formation and subsequent clotting), not a preventive measure for undamaged vessels.

Answer:

A. Heparin from basophils and mast cells, B. Smooth endothelium of blood vessel walls