Why are only COWS kidneys noduled?

Question

My mother in law says no one can answer this

Answer 1

The tubes in a cow's kidney that collect the urine are shorter than in other mammals. Because the collecting tubes or "papillary ducts" are so short, the kidney is divided into more parts than in other mammals, giving it a "noduled" appearance.
From the first web site noted below:
"The organization of the kidney of mammals varies by species. The pelvic organization of the cow lacks long papillary ducts. Urine empties into minor calyces which in turn empty into major calicies. These major calyces empty into the ureter without forming a large pelvis."
The web sites below show images of cow kidneys.

Answer 2

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