The hepatic portal system is the vein that connects the digestive tract and the spleen to the liver (where raw nutrients in blood are processed before the blood returns to the heart). Essentially, it drains the structures fed by the celiac (with the exception of the gonads), anterior mesenteric, gastro splenic, and posterior mesenteric arteries. Thus, the branches of the hepatic portal system closely resemble the branches of many of these arteries, and it is straightforward to investigate them after identifying the arteries. The hepatic portal system is injected with yellow latex in some specimens, which substantially improves its examination. You can trace its branches in an uninjected specimen, but you can also inspect a shark with the system injected momentarily.
Meaning of hepatic portal system
The hepatic portal system is a network of veins that connects the stomach, colon, spleen and pancreatic capillaries to the liver capillaries. It is an essential component of the body’s filtration mechanism. Its primary role is to transport deoxygenated blood to the liver, where it is further detoxified before returning to the heart.
The hepatic portal system is composed of the following components:
- Hepatic portal vein: this is the primary vein that connects the liver to the rest of the body. It develops at the point where the inferior and superior mesenteric veins meet.
- Inferior mesenteric vein: links the colon and rectum to the portal vein.
- Superior mesenteric vein: links the small intestine to the hepatic portal vein.
- Gastrosplenic vein: this tributary is generated by the merger of the splenic and gastric veins from the spleen and stomach, respectively. Within the pancreas, it connects to the mesenteric vein.
The hepatic portal system is designed to eliminate toxins from the body, and it is incapable of detecting those that are intended to aid in this process.
Hepatic Portal vein
The hepatic portal vein is the primary vessel of the hepatic portal system. It is a big vein located in the gastro hepatoduodenal ligament beside the hepatic artery and anterior bile duct. The portal vein of the liver is generated by the union of three major vessels: the gastric, pancreatic, and lien mesenteric veins. They come together to create the hepatic portal vein near the front tip of the pancreas’s dorsal lobe. Recall that the celiac artery also branches at this location. At times, the gastric and lien mesenteric veins fuse to produce a very small channel that subsequently connects to the pancreas mesenteric vein to generate the hepatic portal vein.
The portal venous system is in responsible for transporting blood from various regions of the digestive tract to the liver. For example, substances ingested in the small intestine would be transported to the liver for processing before being transferred to the heart. Numerous medications ingested via the gastrointestinal system are extensively processed by the liver before reaching the general circulation. The first pass effect is the technical term for this phenomenon.
This system does not encompass the whole gastrointestinal tract. The system spans from about the lower oesophagus to the upper anal canal. Additionally, venous outflow from the spleen and pancreas is included. This explains why certain medications can only be administered via specific methods. For instance, nitro-glycerine cannot be ingested but can be administered sublingually. The liver’s detoxifying abilities are sufficient to render the medicine inactive before it reaches the heart. As a result, nitro-glycerine is administered in a manner that circumvents the portal venous system.
The liver gets both oxygenated and deoxygenated blood. As a result, portal blood has a lower oxygen saturation and perfusion pressure than blood from other organs. Blood flows from portal vein branches through spaces between hepatocyte “plates” called sinusoids. Additionally, blood flows from branches of the hepatic artery and mixes with the sinusoids to provide oxygen to the hepatocytes. This solution percolates through the sinusoids and accumulates in a central vein that empties into the hepatic vein. Following that, the hepatic vein empties into the inferior vena cava.
The portal system is a component of systemic circulation in which blood draining from one structure’s capillary bed passes via bigger veins to supply the capillary bed of another structure before returning to the heart.
Simply said, a portal system is a network of blood arteries that begins and terminates in capillaries. The figure below illustrates the body’s blood circulation system. The hepatic portal vein (a component of the portal system) is seen here; this vein originates in a capillary (of the intestines) and terminates in another capillary (of liver).