Dorothy FarrarPfortader
The portal vein collects the venous blood from the unpaired abdominal organs and carries it to the liver. There it mixes with the oxygen-rich blood of the hepatic artery and is made available to the liver cells for metabolism.
Definition
The job of the portal vein, also known as the vena portae, is to collect the blood from the unpaired abdominal organs such as the stomach , small intestine , large intestine , spleen and pancreas and then transport it to the liver. The blood coming from the abdominal organs is venous and therefore low in oxygen. But it is rich in nutrients that were obtained in the digestive process.
Metabolism end products, for example from the breakdown of blood cells in the spleen , are also found in portal vein blood. The metabolism of these nutrients and metabolic end products then takes place in the liver before the blood from the liver is returned to the systemic circulation and finally reaches the right heart via the inferior vena cava .
Anatomy
The portal vein is located behind the pancreas (pancreas) and runs together with the hepatic artery, the hepatic artery, in the hepatoduodenal ligament. Both blood vessels run from the pancreas diagonally upwards to the right and then open into the porta hepatis.
The porta hepatis, also called porta hepatis, is the name of the place on the underside of the liver where, in addition to the hepatic artery and the portal vein, the bile ducts , lymphatic vessels and nerve fibers enter or exit the liver.
The portal vein arises from the confluence of the splenic vein (Vena splenica) and the upper mesenteric vein, the Vena mesenterica superior. The superior mesenteric vein transports oxygen-poor but nutrient-rich blood from the jejunum, ileum, appendix, ascending large intestine (ascending colon) and transverse large intestine (colon transverse). Parts of the venous blood from the pancreas and duodenum are also disposed of via the superior mesenteric vein.
The splenic vein carries venous blood from the spleen, parts of the stomach, the pancreas and the inferior mesenteric vein. The inferior mesenteric vein carries blood from parts of the transverse colon, from the descending branch of the large intestine (colon descendens) and from the upper rectum. In addition, the portal vein transports blood from the gastric veins, the pyloric vein, the cystic vein and the paraumbilical veins.
After entering the liver through the porta hepatis, the liver divides. One branch leads to the left and the other branch to the right lobe of the liver. In the respective liver lobe, the branches then branch into other small vessels up to the so-called liver sinusoids. The liver sinusoids are the smallest vessels located between the liver cells, the hepatocytes.
Function
The nutrient-rich blood originating from the digestive tract is first collected via the portal vein and then brought together to the liver. This venous blood circulation is also known as the portal vein circulation.
The portal circulation ensures that the blood from the unpaired abdominal organs first passes through the liver before it is then fed into the systemic circulation. There are several reasons for this. On the one hand, the nutrients absorbed from the food go directly to the liver via the portal vein and can be processed there.
Excess glucose is stored in the liver in the form of glycogen, and the liver also stores fats, numerous vitamins and iron . Any ingested toxins also travel from the gastrointestinal tract to the liver. There they are broken down and then fed into the body’s circulation in a harmless form.
Likewise, many drugs are first metabolized in the liver before they reach their actual target organs. This process is also known as the first pass effect. The first-pass effect plays an important role in the correct dosing of drugs.
Diseases
- liver fluke
- portal hypertension
- Portokavale Anastomosen
Since the liver carries all the venous blood of the unpaired abdominal organs, it is also a possible transport route for pathogens. Liver flukes or fox tapeworms, for example, reach the liver through the portal vein.
If the blood accumulates in the portal vein, this is referred to as portal hypertension. This is usually caused by damage to the liver, such as fatty liver or liver cirrhosis . Due to the congestion, the blood from the unpaired abdominal organs cannot flow through the portal vein as usual, but has to switch to other blood vessels.
There are various blood vessels that lead from the abdominal organs directly to the superior or inferior vena cava, allowing blood flow bypassing the liver. These bypasses are also referred to as portocaval anastomoses.
Examples are the periumbilical veins, the veins of the esophagus or the rectal veins. These veins are actually not designed for such large amounts of blood. Accordingly, they expand and may burst under certain circumstances. Especially an enlargement of the veins of the esophagus can be life-threatening. If these so-called esophageal varices bleed, the patient can bleed to death within a very short time.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.