Portal circulation

Portal circulation refers to the part of the circulatory system that carries blood from the gastrointestinal tract, gallbladder, pancreas, and spleen to the liver. This system is unique because it involves two consecutive capillary beds before the blood returns to the heart.

Anatomy

The portal circulation begins in the capillaries of the gastrointestinal tract, spleen, pancreas, and gallbladder. Here, blood collects into the portal vein, which splits into left and right branches in the liver. These branches further divide into tiny capillaries called sinusoids. After passing through the sinusoids, the blood collects into the hepatic veins, which drain into the inferior vena cava and return the blood to the heart.

Function

The primary function of the portal circulation is to deliver nutrients and chemical signals from the gastrointestinal tract to the liver for processing. This allows the liver to regulate the levels of many substances in the body, including glucose, amino acids, and lipids. The portal circulation also carries toxins and other harmful substances from the gastrointestinal tract to the liver, where they can be detoxified and excreted.

Clinical significance

Disorders of the portal circulation can lead to serious health problems. For example, portal hypertension is a condition characterized by increased pressure in the portal vein, often due to liver disease. This can cause blood to back up into other veins, leading to complications such as esophageal varices and ascites. Another condition, portal vein thrombosis, involves a blood clot in the portal vein and can lead to intestinal ischemia or liver failure.

See also

• Hepatic portal system
• Hepatic artery
• Hepatic veins
• Liver