Which part of the Loop of Henle is more permeable to water?

Correct Answer: C

Rationale: The thin descending limb is highly water-permeable osmosis concentrates filtrate (e.g., medullary gradient). Thick ascending limb is impermeable actively pumps NaCl. Thin ascending limb is less permeable salt exits. Thick descending isn't a segment error. Water permeability distinguishes the thin descending, critical for countercurrent multiplier, unlike salt-focused or misnamed parts.

Correct Answer: A

Rationale: Glomerular hydrostatic pressure (~55 mmHg) pushes fluid out drives filtration (e.g., Starling force). Back into vessels is oncotic/capsular opposes. No effect ignores its role false. Varying with oncotic misaligns independent. Outward push distinguishes it, critical for GFR, unlike opposing or neutral errors.

Correct Answer: A

Rationale: The proximal tubule is the primary site for organic ion secretion e.g., urate, creatinine via transporters (e.g., OATs). Loop of Henle concentrates minimal secretion. Distal tubule secretes H /K less organic. Collecting duct adjusts not primary. Proximal dominance distinguishes it, key to waste excretion, unlike later segments.

Correct Answer: B

Rationale: Proximal tubule reabsorption is isosmotic water follows Na (e.g., ~65% reclaimed), maintaining osmolarity. Leaky epithelium is permeable false. Na uses transcellular/paracellular not only transcellular. Chloride rises in lumen drives later reabsorption. Isosmotic nature distinguishes it, key to bulk reabsorption, unlike permeability or ion errors.

Correct Answer: B

Rationale: PCT fluid is isosmotic water follows Na reabsorption (e.g., ~65% reclaimed), matching plasma. Hyperosmotic requires concentration later nephron. Hypoosmotic needs dilution ascending limb. ADH affects distal not PCT. Isosmotic balance distinguishes it, key to proximal bulk flow, unlike osmotic shifts.