Although veins normally carry blood directly from capillaries to the heart, in
amphibians, this plan is interrupted by capillary beds in two portal systems –
the hepatic and renal portal systems. The hepatic portal system consist of two
main vessels, the ventral abdominal vein (1) in the ventral body wall (often
broken during dissection), which collects blood from the pelvis, and the hepatic
portal vein, which receives blood from the stomach (gastric vein), intestine
(mesenteric vein) and spleen (splenic vein). The renal portal system conducts
blood from the hind legs directly to the kidneys via the renal portal veins.
Other labeled structures on the image include the heart (2) and three lobes of
the liver (3).