Theory 42/Biology & physiology/Urine concentration
Concentration Is Loop Against Flow
The claim
Maximum urine concentration is set by the ratio of loop of Henle length to tubular flow rate, so a longer loop concentrates more at the same flow.
01Mechanism
The countercurrent multiplier builds a gradient proportional to length while flow washes it out.
02Prediction
Concentration should track the ratio.
03Refutation
Concentration tracking hormone level would remove loop geometry.