Advanced Dental Admission Test (ADAT)

What is the role of antithrombin in the coagulation process?

1. To promote blood clotting

2. To inhibit thrombin and factor Xa

3. To activate factor VII

4. To enhance fibrinogen conversion

The correct answer is: To inhibit thrombin and factor Xa

Antithrombin plays a critical role in the regulation of the coagulation process by inhibiting the activity of key pro-coagulation factors, specifically thrombin and factor Xa. Thrombin is essential for converting fibrinogen to fibrin, which is a major component of blood clots, and factor Xa is crucial for the activation of prothrombin to thrombin, thereby facilitating clot formation. By inhibiting thrombin and factor Xa, antithrombin serves as a natural anticoagulant, helping to prevent excessive blood clotting and maintain hemostatic balance in the bloodstream. This action is vital for preventing thrombotic disorders, ensuring that while the body can effectively stop bleeding when necessary, it does not form clots unnecessarily, which can lead to complications like thrombosis. The other options describe functions that do not pertain to antithrombin’s activity specifically. Promoting blood clotting or enhancing the conversion of fibrinogen would increase clotting activity, while activating factor VII is part of a different pathway in coagulation that involves tissue factor and does not relate to the inhibitory function of antithrombin. Thus, the role of antithrombin is clearly defined by its ability to inhibit thrombin and factor