Which of the following statement is true ? (AIIMS MAY 2011)
|A||Fluid coming from the descending limb of loop of henle is hypotonic|
|B||Descending limb of loop of henle is permeable to solutes|
|C||If clearance of substance is greater than GFR, then tubular secretion must be present|
|D||Clearance of a substance is always less than GFR if there is tubular secretion|
I. The explanation is based on the basic definition and the concept of clearance.
II. The clearance of a substance which is freely filtered and neither secreted nor reabsorbed (e.g. inulin clearance) gives the value of GFR.
III. Any substance which has a clearance greater than that of inulin must be getting secreted in addition to being freely filtered.
IV. One of the most important aspects of counter-current multiplier system is the differential permeability characteristic of descending thin segment (DTS) and the ascending thin segment of the loop of Henle (ATS):
a. DTS : is permeable to water but not solutes
b. ATS : is permeable to sodium but not water
V. Due to this, the tubular fluid in the descending loop gets hypertonic whereas in the ascending limb, the tubular fluid becomes dilute.