- A It filters plasma proteins out of the blood as it enters the glomerulus using size-selective podocyte slits rather than any salt-gradient mechanism in the medulla
- B Creates a hyperosmotic medullary gradient by active NaCl transport in thick ascending limb, enabling concentrated urine production
- C It reabsorbs all filtered glucose completely via SGLT transporters in the descending limb, a transporter and nephron segment actually responsible for glucose, not osmotic gradient formation
- D It synthesizes and releases the enzyme renin into the afferent arteriole, a hormone-secreting function carried out by granular cells, not the loop of Henle itself
Correct answer: B. Creates a hyperosmotic medullary gradient by active NaCl transport in thick ascending limb, enabling concentrated urine production
Explanation: Counter-current multiplier: thick ascending limb actively pumps NaCl without water (impermeable to water). This concentrates medullary interstitium. Descending limb (permeable to water) loses water. Together they create an osmotic gradient to concentrate urine.
Concept context
Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.
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