If the diameter of a blood vessel decreases, then the resistance will ___, thus blood pressure will ___

Correct Answer: C

Rationale: Per Poiseuille’s law, decreased diameter increases resistance (C, ∝ 1/r⁴), raising BP if flow is constant. A, B, D mismatch resistance-BP relationship.

Correct Answer: C

Rationale: The foramen ovale (C) is the fetal atrial opening, shunting blood from right to left atrium to bypass lungs. Ductus venosus (A) shunts liver, ductus arteriosus (B) lungs, circle of Willis (D) is cerebral.

Correct Answer: B

Rationale: The first branches of the aorta are the coronary arteries (B), arising from the aortic root to supply the heart. Brachiocephalic (A), carotid (C), and subclavian (D) branch from the aortic arch.

Correct Answer: C

Rationale: Blood from the right ventricle exits via the pulmonary valve (C) to the pulmonary artery. Tricuspid (A) is inflow, bicuspid (B) is left-sided, and aortic arch (D) is systemic.

Correct Answer: D

Rationale: the absolute refractory period (~0.25-0.3 s) lasts through systole (A), is longer than skeletal muscle (B, ~0.002 s), prevents restimulation (C), and matches the action potential (D).