In the medulla of the kidney, the medullary collecting tubules coalesce to form:

Correct Answer: C

Rationale: Papillary ducts (ducts of Bellini) form from collecting tubules in the medulla, draining into calyces not area cribrosa (papilla tip), rays (cortex), or calyces (collecting). This specifies urine collection, key for excretion, contrasting with earlier structures.

Correct Answer: E

Rationale: Mesangial cells are pericytes, contract, have receptors (AII, ANF), and phagocytose all true. This comprehensively describes their role, critical for glomerular dynamics, contrasting with partial functions.

Correct Answer: D

Rationale: Collecting ducts have principal (water) and intercalated (acid-base) cells not lacis (JGA). This specifies cell types, critical for concentration, contrasting with JGA inclusion.

Correct Answer: D

Rationale: Arteriola recta spuria (false) arise from efferent arterioles not interlobar, interlobular, or afferent. This specifies medullary supply, critical for countercurrent, contrasting with other origins.

Correct Answer: D

Rationale: Ducts of Bellini are large (200-300 μm), columnar-lined, and empty at area cribrosa all true. This fully describes papillary ducts, key for urine delivery, contrasting with partial features.