Question

the type of portal system absent in human

Answer 1

renal portal system is ansent in human
hepatic portal system and hypophysial portal system is present in human.

Answer 2

Since humans are mammals, the renal portal system is absent in them.

Due to the process of evolution, the mammals lost their renal portal systems.

The fish and amphibians have them, the birds have them to some extent, and finally, the mammals do not have them at all.

There are four chambers in the mammalian heart that separates the oxygenated and de-oxygenated, and this allows to separate the blood.