Functions and Anatomy of the Portal Vein

Liver's portal vein: anatomy, functions and location

The portal vein is used to carry blood from the organs into your abdomen to your liver. This blood should pass through your liver for the filtration process before it returns to your body’s general circulation. The portal vein in your body plays an important role in draining many smaller veins in your abdominal area that help in sending the blood into your liver.

What is a portal vein?

The portal vein in your body is mainly a blood vessel that carries blood to the liver from the gastrointestinal tract, which includes intestine, spleen, stomach and pancreas. Than you liver filter and process this blood and the waste product is discarded. This blood than return back to heart and recirculates through your body. 

Blood veins in your body usually carry blood towards your heart. However, your hepatic portal system (portal venous system) is a little different from this rule. These veins in the system send blood to your liver and then the filtered blood to your heart. In the hepatic portal system, the portal veins are the main blood vessels. To know more about the portal vein and its functions, you have to learn a little bit about the portal venous system.

What is a portal venous system (hepatic portal system)?

The portal venous system in your body is a complex system of veins that mainly drain blood from the following organs in your abdominal area. 

• Large intestine
• Small intestine
• Pancreas
• Stomach
• Spleen
• Gallbladder

There are many small veins in you portal venous system that collect blood from all of these organs and deliver it to the portal vein, though you may think of portal vein as a pit lane but it path for blood, that leads towards the liver. Than the collected blood is filtered and processed in liver for necessary maintenance. 

All the blood that reaches to the portal vein is filled with nutrients that are needed to process before your body can use them. The blood also contain toxin and harmful substance you body doe not need. Than you liver filters that blood and remove the toxins, it basically convert all the nutrients that your body can use right away or may be store for later use. After the filtration, the processed blood is than ready to go back to the heart.

 
Functions of the liver

Like all other organs in your body, the liver requires a constant supply of blood to maintain life and a healthy body. The liver has two blood supplies that deliver blood: the portal vein and the hepatic artery. Most of the blood flow that comes into the liver is from the portal vein, which is also responsible for providing most of the oxygen and nutrients to the liver.

The liver’s main function is to filter blood and detoxify many harmful substances, like drugs and other toxins, which are absorbed by your gastrointestinal tract. It also helps to metabolize proteins, fats and carbohydrates that you eat.

Functions of the portal vein

The portal vein is responsible for about 75% of the blood that is delivered from organs in your abdominal area to your liver for processing, as the blood has to be processed before it is released to the rest of the body. This whole system is a portal venous system. The portal vein is the main passageway for blood to enter your liver, as it carries nutrient-rich blood from the organs in the gastrointestinal tract and spleen to the liver. As all the veins in the system ultimately cover and lead to your portal vein, it is very important to keep it healthy and working because it is best for the whole system.

Tributaries of the portal vein

Your portal vein is a complex structure with several veins or tributaries that drain into it. This structure mainly includes: 

Superior mesenteric vein: The primary function of the superior mesenteric vein is to drain the blood from the central part of the gastrointestinal tract. It includes your small intestine, transverse and ascending parts of your colon, caecum and central parts of your stomach. 

Splenic vein: The splenic vein is a part of hepatic portal system, it is blood vessel that drains blood from spleen, parts of pancreas and the superior portion of the stomach (fundus).

Gastric veins: The position of the gastric vein falls along the lesser and greater curvatures. The gastric vein either drains directly or indirectly into the portal vein system. It mainly drains your stomach.

Inferior mesenteric vein: The inferior mesenteric vein is a blood vessel that mainly drains blood from the large intestine in the portal system. 

Cystic veins: The cystic veins in portal system is usually small multiple veins that drains blood from the gallbladder and the cystic dust.

Where is the portal vein located?

Your portal vein starts from the back side of the neck of your pancreas and then comes in front of your inferior vena cava. Generally the portal vein is about 8 cms (3 inches) long in adults. It is located in the upper right quadrant of the belly, which than travel toward the right, and behind your hepatic artery to your liver. After it reach into liver hilum it splits into two branches.

 
What is the anatomy of the portal vein?

A portal vein in the human body forms at the point where the splenic vein and superior mesenteric vein meet. It travels in the upper direction towards the right, behind the hepatic artery, to the liver.  When it enters your liver hilum, The portal vein will split into two branches, and these branches will become your right portal vein and left portal vein. However, these branches will divide into more branches, and those branches will travel to different parts of your liver.

 
Average length of portal vein in human is 8cm long and a maximum of 13mm diameter. It is produced by joining of splenic veins and superior mesenteric veins at the neck of pancreas. Before reaching to the liver, portal veins will be split into right and left, which can regrow and eventually generate small venous branches and portal venules. 

Variations in anatomy

The variation in anatomy happens when the portal vein trifurcation occurs. This is when the portal vein is split into three instead of two. In this case, the branches are known as:

• Right anterior portal vein
• Left portal vein
• Right posterior portal vein

This change may not be dangerous, but the doctor needs to know about it before performing any kind of surgery and procedures. The healthcare provider will run an imaging exam before the surgery to learn about your anatomy, and you may need to make some changes in the techniques.
 

Conclusion:

Blood needs to be filtered before entering the heart, and the process of filtration is done by the liver. The blood is carried from the organs in the belly with the help of the venous system. However, the portal vein carries most of the blood from the organs to the liver. The portal vein is a complex vein system that connects all the organs and takes blood into the liver to filter and process. Meanwhile, the portal vein is an important part of the human body and needs to be taken care of.