Urea
A) is the waste product with the smallest molecular size in the glomerular filtrate.
B) is in greater concentration at the end of the proximal tubule than in other body fluids.
C) has a clearance rate greater than GFR.
D) both (a) and (b) above are correct.
E) all of these answers.

Question

Quizplus · Accepted Answer

Urea is one of the waste products filtered by the glomerulus in the kidney. Because of its small size, it is freely filtered and very little of it is reabsorbed by the renal tubules. Therefore, its concentration increases along the length of the proximal tubule. The clearance rate of urea is usually higher than the glomerular filtration rate (GFR) since some of the urea is excreted by secretion in addition to filtration. Therefore, both statements (a) and (b) are correct. Choice (e) is incorrect because not all of the answers are correct. Choice (c) is incorrect because the clearance rate of urea is usually less than the GFR.