Q- Which of the following anticoagulant medications works by binding to thrombin and inhibiting it?
A- Heparin
B- Hirudin
C- Ticlopidine
D- Warfarin
B- Hirudin- Hirudin is a direct thrombin inhibitor that binds to thrombin and blocks its activity. Heparin acts indirectly via antithrombin; ticlopidine inhibits platelet aggregation; and warfarin blocks vitamin K-dependent clotting factor synthesis.
Q- In cases of atrial septal defect (ASD), foramen ovale is formed by incomplete development of which one of the following structures?
A- Ostium primum
B- Ostium secundum
C- Septum primum
D- Septum secundum
D- Septum secundum- The foramen ovale is created by the incomplete development of the septum secundum, which leaves an opening that allows right-to-left shunting in the fetus. Abnormal resorption of the septum primum can also lead to secundum-type ASDs, but the foramen ovale itself exists because the septum secundum does not fully close.
Q- Which of the following regions of the brain is most likely affected in patients with Huntington’s disease?
A- Anterior frontal lobe
B- Caudate nucleus
C- Substantia nigra
D- Temporal lobe
B- Caudate nucleus- Huntington’s disease is characterized by degeneration and atrophy of the caudate nucleus, leading to chorea, psychiatric changes, and cognitive decline.
Hello Dr Muhammad
Had you applied for USMLE Step 1?
USMLE. Step. 1