Physiology 3120 Lecture Notes - Stem-Loop, Kangaroo Rat, Extracellular Fluid
26 Nov 2011
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Document Summary
Counter-current multiplier system: high osmolarity of the medulla is essential for concentrating urine, mechanism. At the same time, water leaves the descending loop, and salt leaves the ascending loop, so the interstitium is more concentrated than normal. As the fluid flows, water from descending loop leaves, and salt from the ascending loop leaves, which forms a gradient: arrangement of vasa recti. Run in parallel to each other, and anti-parallel to the loop of henle. Run in hairpin loop, which really maintains concentration gradient. As it moves through the medulla, the blood becomes more concentrated, but never equalizes with the interstitium because the plasma moves too fast (except at the bottom of the loop. Urea = organic ion that is a waste product of the body. 50% excreted in urine; 50% is kept in the medulla of the kidney, and contributes to medullary. During low protein intake, decreased ability to concentrate urine (can"t make urea)
