Portal venous system
one capillary bed draining into another through veins
In the circulatory system of vertebrates, a portal venous system occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are considered part of the portal venous system.
Most capillary beds drain into venules and veins which then drain into the heart, not into another capillary bed. There are three portal systems, two venous: the hepatic portal system and the hypophyseal portal system; and one arterial (one capillary system between two arteries): the renal portal system. Unqualified, portal venous system usually refers to the hepatic portal system. For this reason, portal vein most commonly refers to the hepatic portal vein.
The functional significance of such a system is that it transports products of one region directly to another region in relatively high concentrations. If the heart were involved in the blood circulation between those two regions, those products would be spread around the rest of the body.
In humans
The human hepatic portal system delivers about three-fourths of the blood going to the liver. The final common pathway for transport of venous blood from the spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.
The public source identifies “Portal venous system” as one capillary bed draining into another through veins. This brief keeps that definition visible, then builds a research path around Portal, venous and system.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jan 18, 2026. The linked authority identifier is Q2394016. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Portal venous system” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.