Chapter 50 – Osmotic Regulation and the Urinary System
29. What animal has kidneys that are so efficient that it never has to drink water and can
obtain all of its water from its food?
30. Gary has a kidney stone lodged in his ureter. Where will the radiologist find the kidney stone on an x-ray?
31. How does the loop of Henle enable the mammalian kidney to produce hypertonic urine?
I-The ascending limb of the loop actively extrudes Na+.
II-The descending limb interacts with the ascending limb to raise the osmolarity of the
extracellular fluid in the renal medulla.
III-The concentration is further enhanced by the presence of urea, which draws water out of
the collecting ducts by osmosis.