portal circulation

Ads

Hepatic portal vein

The hepatic portal vein (often portal vein for short) is a portal vein in the human body that drains blood from the digestive system and its associated glands. It is one of the main components of the hepatic portal venous system.

Structure

It is formed by the union of the

and divides into a right and a left branch immediately before entering the liver.

Note that the portal vein drains blood into the liver, not from the liver. The blood enters the liver via the portal vein, is then cleaned by the liver, before draining into the inferior vena cava via the hepatic veins. The inferior mesenteric vein usually does not directly connect to the hepatic portal vein; it drains into the splenic vein.

Portal vein branches into many generation of vessels that open into hepatic sinusoids. Blood is recollected into the hepatic vein and enters the inferior vena cava.

Tributaries

The tributaries of the hepatic portal vein include:

Physiology

Almost all of the blood coming from the digestive system drains into a special venous circulation called the portal circulation. This is because it contains all the nutrients and toxins that have been absorbed along the digestive tract from ingested food. Before these absorbed substances can go into the systemic circulation (the main blood circulation in the body), it must be filtered first to remove or detoxify toxic substances first. This filtering and detoxification is one of the functions of the liver.

Role in disease

Increased blood pressure in the portal vein, portal hypertension, occurs in liver disease (mainly cirrhosis), and may lead to various complications (ascites, esophageal varices, spontaneous bacterial peritonitis). A disruption of the hypothalamo-pituitary portal veins is referred to as Pickardt syndrome (suprasellar failure).

Portacaval anastomosis

The portal venous system has several anastomoses (portacaval anastomosis) with the systemic venous system. These are of consequence because in cases of portal hypertension these anastamoses may become engorged, dilated, or varicosed and subsequently rupture.