Question

Assertion (A): In humans, major amount of water is absorbed by the tubular part of nephron.

Reason (R): Absorption of water depends on the dissolved waste to be excreted from the body.

Options

• Both A and R are true and R is the correct explanation of A.

• Both A and R are true but R is not the correct explanation of A.

• A is true but R is false.

• A is false but R is true.

Answer 1

Both A and R are true and R is the correct explanation of A.

Explanation:

The assertion is true because out of nearly 180 litres of initial filtrate formed daily, the vast majority (about 99%) of the water is reabsorbed as it flows through the tubular segments of the nephron (like the proximal convoluted tubule and collecting duct). The reason is also true and provides the correct explanation because water reabsorption is biologically adjusted based on the concentration of dissolved metabolic wastes to be excreted. If there is a high amount of dissolved waste or low water volume in the body, the tubules selectively reabsorb more water under the influence of hormones like ADH to concentrate the urine and conserve fluid.