liver anatomy
Introduction
Liver, since it has an essential role in digestion. Our aim in this article is to understand the complete anatomy and the orientation of the Liver. And to do that, We're first going to cover the Function and the Topography of the Liver. And then we're going to look at the external structures of the Liver by going through the lobes, margins, and grooves we have on the surface of the Liver, and then we're going to talk about porta Hepatis, along with how the Liver is fixated. Basically, going through the covering and the ligaments you'll find around the Liver. The function of the Liver:
Information about liver:
So the Liver, or The Hepar in Latin, is the largest internal organ in the body. It lies on the right side of the belly and weighs approximately 1.5 kilograms, so it's pretty heavy.
Main Role of Liver:
The Liver's main job is to filter and purify the blood coming from the digestive tract before entering it to the rest of the body. And it does that through the portal system. And even if you're not familiar with the portal system yet, it is quite important to understand this concept to fully understand the anatomy of the Liver.
Portal System:
And it's quite simple, the portal system is just veins that drain the nutrients of food from the digestive tract and waste products from the spleen. And when all of those veins meet, they become the portal vein, which will go through the Liver.
Working of Portal System:
The Liver then filters the blood from harmful substances, then sends the blood further into the systemic circulation through the inferior vena cava. Now, this is a very simplified scheme of the portal system, but I hope you get what I tried to tell you earlier, that it filters the blood coming from the digestive tract.
Liver as a Detoxifier:
The Liver also detoxifies the body by transforming potentially harmful substances such as drugs and alcohol into harmless products to be eliminated in The Bile or Urine. Liver for other Functions:
It also produces cholesterol, which is used for the production of certain hormones, and vitamin D. Many nutrients are stored in the Liver as well, including certain fats and glycogen, and this glycogen can be used in case of low blood sugar ,for example ,So it has many functions. Topography of the Liver:
As always, looking at the anatomy of organs, I always like to start with the topography to have the orientation in our heads. So if we add the lines and look at the topography, meaning the Liver position in relation to the body as a whole.
Location of Liver:
The Liver actually covers the whole upper level of the abdominal cavity within the ribs. You will find it in the right hypochondriac region, the epigastric region, and extend to the left hypochondriac region.
Position of Liver relative to bones:
From a clinical perspective, we visualize the borders of the Liver by using the skeletopy of the Liver. Meaning its position in relation to our bones. As you see right here, the superior border starts at the level of the 10th rib and then extends up to the level of the 4th intercostal Space at the region of approximately the Right midclavicular line. And then goes to the 5th intercostal Space left to the sternum.
End of Liver:
And then it ends at the 6th intercostal Space, so that's the superior border. Then the inferior border is here, and it also starts at the 10th rib at the right side and goes up to the level of the 8th -9th rib, and then continues all the way up to the 6th intercostal Space on the left side, where it ends. And then posteriorly, you'll find it between the 9th thoracic vertebra to the 11th thoracic vertebrae.
So that is the Skeletopy of the Liver. Now let's do the Syntopy of the Liver, meaning its position in relation to other organs.
Syntopy of the Liver:
Let's look at the superior border first. This is the surface we call the diaphragmatic surface because you'll find the perfectly drawn diaphragm resting on it, as you see here. And then the inferior border we call this one the visceral surface, meaning the surface that faces different organs.
Let's look at the superior border first. This is the surface we call the diaphragmatic surface because you'll find the perfectly drawn diaphragm resting on it, as you see here. And then the inferior border we call this one the visceral surface, meaning the surface that faces different organs.
Various other Organs:
You'll find the pylorus of the stomach is very close to the visceral surface of the Liver. But you'll also find the upper part of the duodenum, you find the Colon, you find the right kidney, and you also find the Oesophagus and stomach, the upper part of the stomach lying very close to the superior end of the Liver as well.
External Structures of the Liver:
So that was it for the topography. Let's now continue with the external structures of the
Liver. And we're going to start by looking at the Liver from an anterior view. The first thing that catches your eyes is a distinct ligament in the middle called the Falciform Ligament, and this ligament separates the right and left lobe. Now the Liver has two margins, right? You have the inferior margin projecting downwards. And this margin Is very sharp in shape.
So that was it for the topography. Let's now continue with the external structures of the
Liver. And we're going to start by looking at the Liver from an anterior view. The first thing that catches your eyes is a distinct ligament in the middle called the Falciform Ligament, and this ligament separates the right and left lobe. Now the Liver has two margins, right? You have the inferior margin projecting downwards. And this margin Is very sharp in shape.
Posterior Margin:
And now let's change the angle, and look at the Liver posteriorly. You'll find this rounded posterior margin, which is not as sharp as the inferior one. But an interesting this about the posterior margin is that the whole Liver is covered by ligaments and fat, which we call Peritoneum, except for this area right here on the posterior margin.
Area Nuda:
We call this the Bare Area, or area nuda. It's bare because it's the only place that is not covered by fat tissue. It's in direct contact with the diaphragm cuz, remember, the diaphragm lies on top of the Liver. Important Grooves:
We have three important grooves on the posterior surface.
Right sagittal Groove:
The first one is the right sagittal Groove. And the right sagittal Groove is formed by two other grooves you'll find on the visceral surface of the Liver. And here I want you to imagine the inferior vena cava running in this direction, forming the Groove for the Inferior Vena Cava, right?
So the Right sagittal Groove goes like that. It is formed by the fossa for gallbladder, down here. and it's also formed by the fossa for the inferior vena cava, so that's the right saggital groove it separates the right lobe from all the other lobes you'll find on the posterior view of the Liver
Left sagittal Groove:
And then, we have the left sagittal Groove, and to understand this Groove, we need to know the ligaments. So down here, we have a ligament called the round ligament of the Liver, or ligamentum teres hepatis in Latin.
And above that, there's a ligament called the Venous Ligament of the Liver, or ligamentum venosum. And these two ligaments form the left sagittal Groove, which separates the left lobe from the rest of the lobes.
Transverse Groove:
And then finally, we can see one more Groove called The transverse Groove,
also known as the porta hepatis. Now the porta hepatis is a short depression through which all the neurovascular structures and hepatic ducts enter or leave the Liver. We'll talk more about the porta hepatis in a minute, but let's finish looking at the landmarks on the Liver first.
And then finally, we can see one more Groove called The transverse Groove,
also known as the porta hepatis. Now the porta hepatis is a short depression through which all the neurovascular structures and hepatic ducts enter or leave the Liver. We'll talk more about the porta hepatis in a minute, but let's finish looking at the landmarks on the Liver first.
So the transverse Groove goes like this and separates the caudate lobe from the quadrate lobe.
Now, we have 4 lobes on the posterior side and 2 lobes on the anterior side, right? This is what we call an anatomical Classification or division of the Liver. Dividing it into lobes.
Couinaud's system:
Don't confuse this with something called the Couinaud's system, which divides the Liver into eight functionally independent segments where Each segment has its own vascular inflow, outflow, and biliary drainage. Knowing this makes it easier to surgically operate segments of the Liver away. Keep in mind:
So keep in mind that we have a classification system based on the landmarks we have on the Liver and a classification system that divides the Liver into functionally independent segments. So that's the division of the Liver. Now let's talk a little bit more about porta hepatis,
Porta Hepatis: As we said earlier, the Porta Hepatis, or the transverse Groove, is a short deep depression. And there are a few things that go in and out of this place. The most noticeable structure is the common hepatic duct, but you'll also find the hepatic portal vein and the hepatic artery proper going into the Liver through the transverse Groove. Hepatic Plexus Region:
You'll also find some hepatic lymph nodes and some nerves called the hepatic plexus going through the transverse Groove. And they're all covered by the hepatoduodenal ligament. And this is a ligament that starts off at the Liver and goes down to the duodenum. Therefore it's called The hepatoduodenal ligament. Because it attached the Liver to the duodenum. Coverings of the Liver:
Now let's go over and look at the coverings of the Liver. So the Liver is protected, right? It's protected by something called Tunica fibrosa, which is a fibrous sheath, and then on top of it, it's covered by something called the Peritoneum.
Imagine Sagittal Plane:
Imagine this is a sagittal plane of the abdominal cavity, right? Now for orientation sake, this is the Liver, the stomach, the transverse Colon, the small intestine, and down here is the sigmoid Colon. Now, this is a woman's abdominal cavity, so the uterus is here. Now, we have something called the Peritoneum, and essentially what that Is is a fat layer that is distributed around the abdominal cavity.
2 Regions of Peritonium:
And we divide it into two parts. You have the parietal Peritoneum in Green which covers the surrounding walls of the abdominal cavity. And then you have the visceral Peritoneum, which covers the organs inside the abdominal cavity here in blue. Other layers:
So not only is the Liver covered by Tunica fibrosa, the fibrous layer but it's also covered by the visceral Peritoneum, also called the Tunica serosa. Because the Peritoneum forms a serous membrane, which reduces the friction to surrounding structures, that's why it's good to have this visceral Peritoneum covering the Liver.
Bare Area:
But the whole Liver is not covered. There is actually a place called the bare area. Remember I mentioned this earlier? The bare area, which is in direct contact with the diaphragm. So that's the coverings of the Liver.
So to understand the anatomy of the Liver fully, you now only need to know the ligament that connects the Liver to the diaphragm up there and the ligament that connects the Liver to the other organs. Ligaments Around the Liver:
SO let's look at the ligaments around the Liver in a little more detail. So the ligaments from the Liver to the diaphragm are three or four because the last one has a Right and a Left ligament.
Then there're Four ligaments connecting the Liver to other organs so let's look at the ligaments towards the diaphragm first.
Falciform Ligament:
The first ligament is this one highlighted in green, called the Falciform Ligament, connecting the Liver to the anterior wall. Coronary Ligament:
And then, if we remove the diaphragm, we'll see two distinct ligaments on either side connected to the falciform ligament in the middle, called the Coronary Ligament. This ligament connects to the Liver to the diaphragm.
Bare area:
And then again, don't forget that we have the Bare Area, or area nuda here in the middle. You'll see the coronary ligament surrounding it.
View of Liver Posteriorly:
So if we look at the Liver posteriorly, we'll be able to properly see the coronary ligament surrounding the area nuda. Alright, so now we have two more ligaments we can see on this model.
Triangular Ligaments:
And these are the Triangular Ligaments. We have the Left triangular ligament, and we have a Right triangular ligament. They kind of resemble a triangle, as you see here. Alright, so that was all the ligaments towards the diaphragm.
Ligaments from Liver towards other Organs:
Now let's go over and look at the ligaments that go from the Liver towards other organs. These are four ligaments, and they all start from porta hepatis. I want you to keep that in mind that all the ligament starts at porta hepatis. Hepatogastric Ligament:
So the first one is the Hepatogastric Ligament, and as the name says, it goes from the Liver to the stomach, or in Latin, it goes from the hepar to the gaster. That's why it gets the name lig. Hepatogastricum.
Hepatoduodenal Ligament:
And then the next one is the Hepatoduodenal Ligament, going from the Porta hepatis of the Liver to the duodenum. And remember, as we saw earlier, This ligament contains the bile duct veins, nerves, arteries, and things going in and out from the porta hepatis. So that was the Hepatoduodenal Ligament.
Hepatorenal ligament:
Next, we have the hepatorenal ligament. Renal means kidney, so this one goes from the Liver to the right kidney. And the right kidney is behind here, so it goes like this. Some sources might not mention this ligament, as they consider it a part of the coronary ligament I mentioned earlier, and some sources might do. Keep that in mind. Ligament Teres Hepatis:
And then lastly, we have the round ligament of the Liver. Or Lig. Teres Hepatis. This one projects anteriorly and extends from porta hepatis towards the umbilical ring or the navel. Because It is the remnant of the left umbilical vein during fetal life. So that was all I had for the anatomy of the liver.
