The following blood vessels contain valves EXCEPT

Correct Answer: A

Rationale: Valves in blood vessels prevent backflow, aiding venous return against gravity, but capillaries lack them due to their role in exchange, not directional flow. 'Capillaries,' is correct, as per anatomy texts like Moore's Clinically Oriented Anatomy, which note valves in veins and some venules. 'Veins,' have valves, especially in limbs. 'Venules,' may have valves in larger ones transitioning to veins. 'Vena cavae,' lack valves, but the question's focus on typical presence points to capillaries' exception. Capillaries' thin walls and continuous flow for nutrient exchange exclude valves, making A the accurate answer, distinct from the venous system's structural adaptations.

Correct Answer: C

Rationale: Vitamin K is essential for synthesizing clotting factors (e.g., prothrombin) in the liver. 'Vitamin K,' is correct, per physiology texts like Guyton, preventing bleeding disorders. 'Vitamin A,' aids vision. 'Vitamin B,' encompasses metabolic coenzymes, not clotting. 'Vitamin D,' regulates calcium. Vitamin K's specific role in coagulation cascades makes C the accurate answer.

Correct Answer: C

Rationale: The urinary bladder holds about 600 ml at full capacity, though urge begins earlier. '600 ml,' is correct, per physiology texts like Guyton, varying (400-700 ml) by individual. '200 ml,' is minimal. '400 ml,' is functional but not maximum. '800 ml,' exceeds average. The 600 ml norm balances anatomy and function, making C the precise answer.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.