Outlet of digestive system is present at back of the body but its digestive system at front.

Outlet of urinary system is present at front of the body but its system present at back.

Why do humans have digestive system present at front and kidneys back?

  • $\begingroup$ Rather, I'd think of both the digestive and urinary systems as occurring top-down and inward-out, because gravity helps. $\endgroup$
    – CKM
    May 25, 2018 at 14:34
  • $\begingroup$ Teleologically, one can say the kidneys are fragile and need to be protected from trauma, which does actually occut in the relative safety of the lower ribs and spinat support structure. The GI tract, on the other hand, would be too restricted in the retroperitoneum; it needs to be able to expand (food, gasses, etc.) Realistically, because it evolved that way; all vertebrates have the same basic anatomy (basic, not specific.) $\endgroup$ May 26, 2018 at 3:57

1 Answer 1


I don't claim to have the full answer to why these organs are located in the way they are, but I think these factors have an influence on the anatomy:

1- The urinary system's link with the reproductive system in male mammals: The male reproductive system outlet needs to be located as far to the front as possible in a 4 legged mammal to facilitate sexual function, forcing the urinary system to follow

2- The kidneys are very fragile and need to be protected by the thick back muscles and partly under the rib cage. They would be too vulnerable at the front

3- The urinary system is generally sterile of bacteria, and so is the reproductive system in males, and partially in females. The digestive system isn't sterile in both. The outlet of the digestive system can't be in the front of the genitals in a male as this will increase the risk of urinary infections overall and also genital infections after mating. It can't be in between the urinary and reproductive outlets for the same reason, so it has to be located behind both to cause the least interference with their functions

  • $\begingroup$ Please provide support for your answer. $\endgroup$ Dec 20, 2018 at 14:52

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