The osmotic concentration in the interstitial fluid is primarily due to the presence of $.....$.

Describe the counter-current mechanism.

The shape of vasa recta is

$\text{NaCl}$ from the ascending limb of Henle's loop is exchanged with:

Compare the statements $A$ and $B$.
$\text{Statement } A$: When the urine moves through the descending limb,it becomes hypertonic,and as it passes through the ascending limb of Henle's loop,it becomes hypotonic.
$\text{Statement } B$: The descending limb is permeable to sodium ions,while the ascending limb is impermeable to sodium ions.

If $Henle's$ loop were absent from the mammalian nephron,which of the following is to be expected?