Surgery>>>>>Hemostasis, Surgical Bleeding, and Transfusion
Question 23#

After tissue injury, the first step in coagulation is:

A. Binding of factor XII to subendothelial collagen
B. Cleavage of factor XI to active factor IX
C. Complexing of factor IX with factor VIII in the presence of ionized calcium conversion of prothrombin to thrombin
D. Formation of fibrin from fibrinogen

Correct Answer is A

Comment:

All the listed steps are part of the cascade involved in establishing a firm clot. The process begins with binding of Hageman factor (factor XII) to subendothelial collagen and ends with the conversion of fibrinogen to fibrin. The fibrin forms an insoluble addition that stabilizes the platelet plug.