Vascular resistance is determined by:

Correct Answer: D

Rationale: Vascular resistance is primarily determined by vessel diameter (D), as per Poiseuille’s law (resistance ∝ 1/r⁴), where small changes in radius greatly affect resistance. Length (A) and viscosity (B) contribute but are less dynamic, C is vague, and E (blood pressure) is an outcome, not a determinant.

Correct Answer: D

Rationale: Atherosclerosis is caused by endothelial injury (D is false), leading to plaque formation. Smoking (A), insulin-dependent diabetes mellitus (C), and possibly H. pylori (B, via inflammation) are risk factors.

Correct Answer: B

Rationale: Semilunar valves open when ventricular pressure exceeds arterial pressure (B, ~80 mmHg diastolic) during systole. A is the result, C/D don’t open valves.

Correct Answer: D

Rationale: Blood vessel layers from innermost to outermost are: tunica intima, tunica media, tunica externa (D). A, B, C reverse or misorder the sequence.

Correct Answer: A

Rationale: Peripheral resistance depends on arterial diameter (major), length, and blood viscosity (A). Cardiac output (B), HR/SV (C), and venous factors (D) influence BP, not resistance directly.