The polycystic kidney is due to failure of communication between:

Correct Answer: C

Rationale: Polycystic kidney results from failed DCT-collecting tubule fusion not PCT-DCT, Bowman's-PCT, or calyceal issues; cysts form at this junction. This pinpoints defect, critical for pathology, contrasting with other nephron stages.

Correct Answer: A

Rationale: Renin activates angiotensin cleaves angiotensinogen to angiotensin I (e.g., JGA response to low BP), triggering RAAS. Vitamin D activation is kidney's calcitriol role not renin. RBC stimulation is erythropoietin not renin. Vasoconstriction is angiotensin II downstream. Renin's angiotensin initiation distinguishes it, critical for BP regulation, unlike unrelated or subsequent effects.

Correct Answer: C

Rationale: Transitional epithelium allows bladder expansion stretches with urine (e.g., multilayered, ~500 mL). Rugae aid but aren't primary folds alone insufficient. Villi are intestinal not bladder. Pseudostratified is respiratory not here. Epithelium's stretch distinguishes it, critical for capacity, unlike folds or wrong tissues.

Correct Answer: C

Rationale: Glomerular filtration occurs between glomerulus and glomerular capsule plasma filters into Bowman's space (e.g., GFR). Afferent/peritubular are vascular not filtration site. Efferent/peritubular are post-filtration incorrect. Peritubular/tubule is reabsorption not filtration. Glomerulus-capsule interface distinguishes it, critical for filtrate formation, unlike vascular or tubular errors.

Correct Answer: C

Rationale: Females have lower water percentage (~50% vs. males ~60%) due to more adipose tissue less water-rich than muscle (e.g., fat ~10% water, muscle ~75%). Higher water contradicts fat lowers. Muscle increases water opposite. Lower muscle isn't primary adipose key. Adipose's impact distinguishes it, critical for sex differences, unlike muscle or reverse errors.