Which structure is the first to collect the urine?

Correct Answer: B

Rationale: Minor calyces collect urine from papillae first, before pelvis, ureter, or urethra. This identifies initial collection, key for urine flow, contrasting with downstream structures.

Correct Answer: B

Rationale: Micturition reflex integrates in the sacral spinal cord (S2-S4), not medulla (respiration), hypothalamus (hormones), or lumbar (lower). This locates reflex center, key for bladder control, contrasting with higher regions.

Correct Answer: A

Rationale: Countercurrent multiplier increases NaCl in the medullary interstitium, not decreases, or affects potassium. This defines concentration gradient, key for water reabsorption, contrasting with potassium roles.

Correct Answer: A

Rationale: PCT removal halts reabsorption (65% filtrate), stopping urine formation, not unaffected, concentrated, or diluted. This underscores PCT's role, critical for filtrate processing, contrasting with later adjustments.

Correct Answer: D

Rationale: Kidneys synthesize calcitriol, secrete erythropoietin, and perform gluconeogenesis all apply. This encompasses metabolic roles, vital for homeostasis, contrasting with single contributions.