Regarding the assertion and reason, choose the correct option.
Assertion [A]: The filtrate that moves from the PCT to the loop of Henle, remains isosmotic.
Reason [R]: About 50% of urea is reabsorbed.
Regarding the assertion and reason, choose the correct option.
Assertion [A]: The filtrate that moves from the PCT to the loop of Henle, remains isosmotic.
Reason [R]: About 50% of urea is reabsorbed.
The correct option is C Assertion [A] is True and Reason [R] is True and is a correct explanation to [A].
Not all of the urea in the body gets filtered and excreted in the filtrate (urine); about 50% is reabsorbed even when urea is the substance we are trying to excrete in the first place. This is basically because urea pulls a lot of water along with it (relatively speaking of course compared to ammonia). Leaving it in the filtrate would prevent water reabsorption and we cannot afford to excrete all that water. Therefore, some urea gets reabsorbed, and effectively the filtrate that moves from the PCT to the loop of Henle remains isosmotic, that is, of the same osmolarity as the fluid in the interstitium and plasma, because water has moved out of the fluid in proportion to the solutes that have been absorbed.
Assertion [A] is True and Reason [R] is True and is a correct explanation to [A].
Not all of the urea in the body gets filtered and excreted in the filtrate (urine); about 50% is reabsorbed even when urea is the substance we are trying to excrete in the first place. This is basically because urea pulls a lot of water along with it (relatively speaking of course compared to ammonia). Leaving it in the filtrate would prevent water reabsorption and we cannot afford to excrete all that water. Therefore, some urea gets reabsorbed, and effectively the filtrate that moves from the PCT to the loop of Henle remains isosmotic, that is, of the same osmolarity as the fluid in the interstitium and plasma, because water has moved out of the fluid in proportion to the solutes that have been absorbed.
