The renal portal vein is a form of renal blood flow in lower animals.Its function comes from the tailveinget intokidney, branched intoblood capillaryIt forms a venous network, and then gathers into veins to draw blood backheart。
In fish, the caudal vein divides into two branches and forms a renal portal vein that enters the kidney, and then the main vein exits the kidney.
Renal portal vein of amphibians
In amphibians, part of the blood from the kidney passes through the posterior main vein, and most of it passes through the posterior great vein to the heart.
Renal portal vein of reptiles and birds
In reptiles, because the posterior main vein degenerates, the blood from the kidney is transported by the posterior great vein.In birds, the venous blood from the tail and pelvis enters the left and right renal portal veins, a small part of which enters the renal capillaries, most of which go forward to merge with the iliac veins on each side, and later connect left and right to form the posterior great vein.Therefore, itsRenal portal vein systemIt is incomplete.
Renal portal vein in mammals
In mammals, the renal portal vein system only exists in the fetal period, and then degenerates and disappears.
Influence of disappearance of renal portal vein on mammals
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The disappearance of the renal portal vein will not affect us.Just like we have tails in the embryonic stage, we are born without them.In terms of development, many of them developed according to the original model, and then showed the species specificity.Our inferior vena cava has 2 branches in the femoral part and enters the leg.Above this, branches enter the left and right kidneys.The inferior vena cava is responsible for the blood returning to the heart, so the renal portal vein disappears.
