24.35: Hepatic Portal System
The hepatic portal system, a critical part of our circulatory framework, transports nutrient-laden, deoxygenated blood from the gastrointestinal tract and spleen to the liver. This ingenious system plays an indispensable role in maintaining our body's metabolic equilibrium.
At its core, the hepatic portal vein is the result of a confluence of the superior and inferior mesenteric veins along with the splenic vein. Each of these veins has a unique role. The superior mesenteric vein is responsible for draining blood from the stomach, pancreas, small intestine, and most of the large intestine.
On the other hand, the inferior mesenteric vein, with its branches including the left colic, sigmoid, and superior rectal veins, drains the lower part of the large intestine. The splenic vein, formed by the union of the inferior mesenteric vein, veins from the spleen, the stomach's lateral border, and the pancreas, contributes to this crucial system.
Additionally, the hepatic portal vein receives blood from the left and right gastric veins and the cystic vein of the gallbladder, thereby ensuring a comprehensive collection of nutrient-rich blood.
Once inside the liver, the metabolites in the blood undergo complex processes like glycolysis and beta-oxidation. These processes enable the storage and metabolism of essential biomolecules, thereby aiding in the overall functioning of the body.
The liver also receives oxygenated blood from the hepatic arteries. This oxygen-rich blood mixes with the deoxygenated blood transported by the hepatic portal vein within the liver sinusoids. Finally, the hepatic vein collects this blood from the sinusoids and carries it to the inferior vena cava, completing the intricate cycle of the hepatic portal system.
