The Kidney MaintainsWater Balance
One of the most important functions of the kidney is maintaining the water content of the body and the tonicity of the plasma. Terrestrial animals constantly guard against desiccation, and thus their kidneys evolved to reabsorb most of the water in the glomerular filtrate.
Under normal conditions, a 10-kg beagle that produces 53.3 L of glomerular filtrate every day may reabsorb more than 99% of the water contained in the glomerular filtrate, excreting only 0.2 to 0.25 L of urine. When water deprived, a normal dog is able to produce urine that has seven to eight times the osmolality of plasma, significantly higher than 2000 milliosmoles per kilogram of water (mθsm∕kg H2O). However, the kidney also can produce hypotonic urine in response to a water overload. After a water load, the same dog can excrete urine with an osmolality as low as 100 mθsm∕kg H2O, approximately one-third that of plasma. This chapter discusses how the kidney accomplishes these feats.
More on the topic The Kidney MaintainsWater Balance:
-
Veterinarian -