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Hypothesis and an Animation |
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| Based on information shown in the preceding
video, and experimental findings by a number of investigators, including us,
I shall now present an hypothesis and an animation on how the renal pelvic
peristalsis, by pumping the papilla, might contribute to the concentrating
mechanism. The model deals only with mammals with a relatively long papilla.
The highest degree of urinary concentration is found in mammals with the
longest papilla. In these, the peristalsis has the strongest effect on the
papilla. I suggest that the kidney papilla works as a pump, through alternating positive and negative pressures generated by the peristaltic contractions of the pelvic wall. Water moves into the collecting duct cells as a result of the small positive hydrostatic pressure on the walls of the cells, generated by the peristaltic wave pushing the fluid through the collecting ducts. Fluid moves out of the cells as a result of the negative pressure generated by elastic forces which expands the papilla during the rebound. Fluid is removed from the interstitium by the vasa recta which contains no blood at the time the blood enters. |
The Pelvic Peristalsis |