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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.
In human anatomy, the hepatic portal system or portal venous system is the system of veins comprising the portal vein and its tributaries. The other portal venous systems in the body are the renal portal system , and the hypophyseal portal system .
The portal vein is not a true vein, because it conducts blood to capillary beds in the liver and not directly to the heart. It is a major component of the hepatic portal system, one of three portal venous systems in the human body; the others being the hypophyseal and renal portal systems.
The central vein joins to the hepatic vein to carry blood out from the liver. A distinctive component of a lobule is the portal triad, which can be found running along each of the lobule's corners. The portal triad consists of the hepatic artery, the portal vein, and the common bile duct. [23]
Illustration showing the hepatic portal vein system. The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism at a specific location in the body which leads to a reduction in the concentration of the active drug before it reaches the site of action or systemic circulation.
A portal venous system is a series of veins or venules that directly connect two capillary beds. The two systems in verebrates are the hepatic portal system, and the hypophyseal portal system . An anastomosis is a joining of two structures such as blood vessels.
Port (medical) Portal system. It is installed under the skin, with the tube connected to a vein. External access is with a needle through the yellow membrane. In medicine, a port is a small medical appliance that is installed beneath the skin. A catheter (plastic tube) connects the port to a vein.
Portacaval anastomosis, by contrast, is a veno-venous anastomosis between a vein of the portal circulation and a vein of the systemic circulation, which allows blood to bypass the liver in patients with portal hypertension, often resulting in hemorrhoids, esophageal varices, or caput medusae.
Renal portal system. A renal portal system is a portal venous system found in reptiles, and fish excluding hagfish and lampreys. It is not found in mammals. [1] Its function is to supply blood to renal tubules when glomerular filtration is absent or downregulated. [2]
CRH and TRH are secreted into the hypophyseal portal system and act on different targets neurons in the anterior pituitary. PVN is thought to mediate many diverse functions through these different hormones, including osmoregulation, appetite, and the response of the body to stress.