portal

Examples of portal in the following topics:

• Blood Supply to the Liver

  • In the hepatic portal system, the liver receives a dual blood supply from the hepatic portal vein and the hepatic arteries.
  • In the hepatic portal system, the liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.
  • The majority of capillaries in the body drain directly into the heart, so portal systems are unusual.
  • The hepatic portal system connects the capillaries of the gastrointestinal tract with the capillaries in the liver.
  • A diagram that shows the hepatic portal vein and its territory.

• Hepatic Portal Circulation

  • The hepatic portal system is responsible for directing blood from parts of the gastrointestinal tract to the liver.
  • The hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries.
  • The hepatic portal vein supplies about 75% of the blood the liver requires, with the other 25% supplied by the hepatic artery.
  • Blood from the hepatic artery is oxygenated but nutrient-poor compared to that supplied by the hepatic portal vein.
  • Since blood received from the hepatic portal vein may be contaminated with pathogens such as bacteria, the liver is rich in specialized immune cells called Kupffer cells that detect and destroy foreign organisms.

• The Liver

  • The liver is supplied by two main blood vessels on its right lobe: the hepatic artery and the portal vein.
  • The portal vein brings venous blood from the spleen, pancreas, and small intestine so that the liver can process the nutrients and byproducts of food digestion.

• Transport of Hormones

  • Some endocrine glands secrete into a portal system rather than the systemic circulation that allows for the direct targeting of hormones.
  • For example, hormones secreted by the pancreas pass into the hepatic portal vein that transports them directly to the liver.

• Anatomy of the Liver

  • The liver is connected to two large blood vessels, the hepatic artery and the portal vein.
  • The hepatic artery carries blood from the aorta to the liver, whereas the portal vein carries blood containing the digested nutrients from the entire gastrointestinal tract, and also from the spleen and pancreas to the liver.

• Veins

  • Although most veins take blood back to the heart, portal veins carry blood between capillary beds.
  • For example, the hepatic portal vein takes blood from the capillary beds in the digestive tract and transports it to the capillary beds in the liver.
  • Since this is an important function in mammals, damage to the hepatic portal vein can be dangerous.
  • Blood clotting in the hepatic portal vein can cause portal hypertension, which results in a decrease of blood fluid to the liver.

• The Portacaval Shunt

  • A connection is made between the portal vein, which supplies 75% of the liver's blood, and the inferior vena cava, the vein that drains blood from the lower two-thirds of the body.
  • The most common causes of liver disease resulting in portal hypertension are cirrhosis , caused by alcohol abuse, and viral hepatitis (hepatitis B and C).
  • Less common causes include diseases such as hemochromatosis, primary biliary cirrhosis (PBC), and portal vein thrombosis.

• Hypothalamic-Pituitary Axis

  • This capillary network is a part of the hypophyseal portal system which carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system.
  • A portal system carries blood from one capillary network to another; therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system.
  • The regulatory hormones travel from the hypothalamus through the hypophyseal portal system to the anterior pituitary where they exert their effect.

• Romanesque Art

  • In a significant innovation of the period, the tympanums of important church portals were carved with monumental schemes, often again depicting Christ in Majesty or the Last Judgement but treated with more freedom than painted versions.
  • These portal sculptures were meant to both intimidate and educate the viewer.

• Selling to Consumers

  • Auctions facilitated at a portal, such as eBay, which allows online real-time bidding on items being sold in the Web
  • Classified ads at portal sites such as Craigslist (an interactive, online marketplace where buyers and sellers can negotiate and that features "Buyer Leads & Want Ads")