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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.
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.
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.
The causes for portal hypertension are classified as originating in the portal venous system before it reaches the liver (prehepatic causes), within the liver (intrahepatic) or between the liver and the heart (post-hepatic). The most common cause is cirrhosis (chronic liver failure).
A portacaval anastomosis or portocaval anastomosis is a specific type of circulatory anastomosis that occurs between the veins of the portal circulation and the vena cava, thus forming one of the principal types of portasystemic anastomosis or portosystemic anastomosis, as it connects the portal circulation to the systemic circulation ...
A portosystemic shunt or portasystemic shunt (medical subject heading term; PSS), also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital (present at birth) or acquired condition and occurs in humans as well as in other species of animals.
The hypophyseal portal system is a system of blood vessels in the microcirculation at the base of the brain, connecting the hypothalamus with the anterior pituitary. Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland. The capillaries in the portal system are ...