hepatic portal system

Examples of hepatic portal system 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 hepatic arteries.
  • In the hepatic portal system, the liver receives a dual blood supply from the hepatic portal vein and hepatic arteries.
  • Oxygen is provided from both sources; approximately half of the liver's oxygen demand is met by the hepatic portal vein, and half is met by the hepatic arteries.
  • The majority of capillaries in the body drain directly into the heart, making portal systems unusual.
  • The hepatic portal system connects the capillaries of the gastrointestinal tract with the capillaries in the liver .

• 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.

• Transport of Hormones

  • The endocrine system is a system of ductless glands that secrete hormones directly into the circulatory system to be carried long distances to other target organs that regulate key body and organ functions.
  • 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.
  • Once within the circulatory system a small proportion of hormones circulate freely, however the majority are bound with a transport protein.
  • Describe the way in which hormones are transported in the endocrine system

• 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.
  • Systemic veins - Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

• Principal Veins

  • In the circulatory system, veins are blood vessels that carry blood towards the heart.
  • The above veins form part of the systemic circulatory system.
  • The renal and hepatic veins from the kidneys and liver respectively also feed into the inferior vena cava.
  • The hepatic portal vein carries blood from the gastrointestinal tract to the liver.
  • The portal vein is often described as a false vein because it conducts blood between capillary networks rather than between a capillary network and the heart.

• Associated Organs

  • The pancreas, liver, and gallbladder are the essential associated organs of the digestive system.
  • 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.
  • The hepatic veins drain directly into the inferior vena cava.
  • These eventually drain into the right and left hepatic ducts, which in turn merge to form the common hepatic duct.

• Anatomy of the Liver and Gallbladder

  • It 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 digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas to the liver.
  • Each lobule is made up of millions of hepatic cells which are the basic metabolic cells of the liver.
  • The neck tapers and connects to the biliary tree via the cystic duct, which then joins the common hepatic duct to become the common bile duct.

• Liver Function

  • The human liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs.
  • The liver is responsible for immunological effects, acting as a 'sieve' for antigens carried to it via the portal system.
  • This type of tissue is most common in alcoholic hepatitis (prevalence of 65%) and alcoholic cirrhosis (prevalence of 51%).

• 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.

• Portals of Microbe Entry

  • In droplet contact and other airborne transmission it is generally the respiratory system through the nose, mouth, or eye surfaces.
  • Sexually transmitted diseases such as HIV and Hepatitis B are thought to be transmitted through unprotected sexual intercourse (including anal and oral routes), contaminated blood transfusions, sharing hypodermic needles, and from mother to child during pregnancy, delivery, or breastfeeding.