I was reading about nephrons in my physiology book when i came across this-

The efferent arterioles and peritubular capillaries technically constitute a portal system

But according to Wikipedia, renal portal system is absent in mammals. Can someone please explain this contradiction?

Edit 1: Could it be that humans are an exception to the case and do contain a renal portal system?

Edit 2: When we were discussing this in class, the my lecturer did say, "They are like portal sytems."

Why is human renal portal system not considered a portal system? Although, it connects two capillary beds (efferent arterioles and peritubular capillaries)

Edit 3- Some sites do say that the capillary beds that connect generally belong to different organs. Could this be responsible for exclusion of human renal portal sytem?

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    $\begingroup$ I think it is a semantic disagreement. Your physiology book says "technically", which suggests that the author knows the renal capillaries are not the same kind of "portal" system found elsewhere. Humans are not exceptional mammals. $\endgroup$
    – kmm
    Sep 24, 2016 at 3:25
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    $\begingroup$ @kmm point taken, but what differentiates it from a portal system? $\endgroup$ Sep 25, 2016 at 1:18
  • 1
    $\begingroup$ You should ask your lecturer why they say "are like a portal system" and not "are a portal system". The distinction seems to matter to them. I don't care much for semantic details. $\endgroup$
    – kmm
    Sep 25, 2016 at 17:59
  • $\begingroup$ Unfortunately, my lectures on the topic have already ended and currently it is our prep time for the examinations. I know this to be just another semantic disagreement but I am curious to find out why. $\endgroup$ Sep 25, 2016 at 18:01


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