Image Based Question – 65212

In the absence of vasopressin, this part marked with (3) reabsorbs the greatest fraction of filtered water?

A. Proximal tubule

B. Distal tubule

C. Loop of Henle

D. Collecting duct

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Correct Answer » A Explanation

This structure is Proximal tubule of nephron

• Proximal tubule is highly water permeable.

• Approximately, 65% of the filtrate is reabsorbed, driven by active transport.

• As ions are reabsorbed water follows by osmosis.

Action of vasopressin:

• Vasopressin influences water permeability only in the distal and collecting tubules.

• It has no influence over the 80% of the filtered water that is reabsorbed without control in the proximal tubule and loop of henle.