Question

This is an anti-clotting substance which we produce to dissolve clots and prevent inappropriate intravascular clotting (thrombus)

. a. Thrombin

b. Heparin

c. Histamine

d. Factor X

e. Fibrinogen

Answer 1

Option B is the appropriate answer.

Heparin is an anti-coagulant found in the human body which prevents intravascular blood clots formation. Heparin is present within the secretory granules of the mast cells and is released under conditions of tissue injury in the vasculature. Heparin exerts its action by binding to the enzyme inhibitor antithrombinIII and activating it which in turn results in inactivation of thrombin. Heparin also inhibits other proteases involved in blood clotting notably Factor-Xa. Inactivation of thrombin leads to stoppage of fibrin formation and thrombin induced activation of platelets, Factor VIII and Factor V preventing blood clotting. It is also used as a blood thinner to prevent thromboembolisms.

Thrombin, Factor X, Fibrinogen all are included in the blood coagulation cascades. Histamine does not have any role in blood clotting but is also another chemical mediator found in mast cells and upon secretion leads to type-I hypersensitivity

Reference- Guyton's textbook of medical physiology