Anatomy of the abdominal viscera: Liver, biliary ducts and gallbladder
AssessmentsAnatomy of the abdominal viscera: Liver, biliary ducts and gallbladder
USMLE® Step 1 style questions USMLE
A group of investigators are studying the gastrointestinal ligament and the structures housed within. They discover the hepatoduodenal ligament contains the portal triad, which consists of the proper hepatic artery, hepatic portal vein, and common bile duct. Which of the following structures form the hepatic portal vein?
Content Reviewers:Viviana Popa, MD, Kaitlin Marshall, M.Sc., B.Sc, David Clay, MSc, BSc
Contributors:Kaia Chessen, MScBMC, Mathew Pietri, Sam Gillespie, BSc, Evode Iradufasha, MD
The liver is quite an amazing organ, and fact is, the rumors you heard are true - it can actually regenerate itself! If that wasn’t enough, it also plays a major role in digestion, by producing bile, storing energy, detoxifying toxic substances and producing proteins. Let’s get started and look more at the liver along with the other associated organs and structures that help with digestion!
The liver is a large intraperitoneal organ located mostly in the right hypochondriac and epigastric regions of the abdomen, deep to the 7th to the 11th ribs. It sits just to the right of the stomach, with some of the liver covering its anterior surface.
It is superior to the duodenum, right side of transverse colon, and right colic flexure. Most of the liver is anterior to the lesser omentum; and it is anterosuperior to the right kidney and adrenal gland.
The liver has many important functions, including the production of bile to aid in fat digestion, reception and metabolization of absorbed products from digestion, detoxification of toxic substances received from digestion, storage and release of carbohydrates, as well as the production of proteins - primarily plasma proteins such as albumin and clotting factors.
When you look closely, the human liver is actually divided grossly into four parts, referred to as lobes. There is a larger right lobe, which is separated from a smaller left lobe by the falciform ligament. Then comes the caudate as well as the quadrate lobes, which are anatomically included in the right lobe.
Now, the liver is surrounded by potential spaces, which are referred to as hepatic spaces. These spaces usually only contain a small amount of peritoneal fluid, which serves as a lubricant between two membranes in close contact. The hepatic spaces include the right and left subphrenic recesses which are extensions of the peritoneal cavity located on the anterosuperior aspect of the liver, and are separated by the falciform ligament.
Next is the subhepatic space, which is located between the liver and the transverse colon. This space connects with the hepatorenal recess which extends posterosuperiorly from the subhepatic space between the liver and the right kidney.
All right, now let’s look at the two main surfaces of the liver. First, is the diaphragmatic surface which is in direct contact with the diaphragm and is smooth and dome-shaped. Second, is the visceral surface, which is an irregular surface molded by neighboring organs such as the gallbladder and the biliary ducts.
The diaphragmatic surface is covered by visceral peritoneum, except on its posterior aspect, which is known as the bare area. The bare area of the liver is in direct contact with the diaphragm; however, it’s surrounded by reflections of the visceral peritoneum, which form the upper and the lower layers of the coronary ligament.
Coronary means crown, so this ligament surrounds the superior surface of the liver like a crown. These layers of the coronary ligament fuse together on the right to form the right triangular ligament, and on the left to form the left triangular ligament.
The liver is divided into right and left lobes by the falciform ligament which originates from the ventral mesentery of the embryological foregut. In its inferior free margin, this ligament contains the ligamentum teres hepatis, which translates as ‘the round ligament of the liver’. This is the remnant of the fetal umbilical vein, which used to carry oxygen-rich blood from the placenta to the fetal liver.
All right, now let’s have a look at the grooves and impressions on the visceral surface of the liver created by the close contact with other organs. First, there are two remarkable grooves, called the right and left sagittal fissures on the posteroinferior surface of the liver. These are connected by the porta hepatis, a short transverse fissure where most hepatic vessels enter and leave the liver. Together, they look a bit like the letter “H”.
The right sagittal fissure contains a fossa for the gallbladder anteriorly, and it continues as the groove for the inferior vena cava along the posterior surface. The groove for the inferior vena cava also extends into the diaphragmatic surface of the liver.
The left sagittal fissure, also known as the umbilical fissure contains the fissure for the round ligament anteriorly and continues posteriorly with the fissure for the ligamentum venosum. The ligamentum venosum was actually called the ductus venosus during fetal life, and its role was to shunt blood from the umbilical vein to the inferior vena cava, bypassing the fetal liver.
Now, there is also the hepatogastric ligament, which is actually part of the lesser omentum that extends from the fissure of the ligamentum venosum to the lesser curvature of the stomach.
The free edge of the lesser omentum, located posteroinferiorly to the right is called the hepatoduodenal ligament which extends between the porta hepatis and the proximal part of the duodenum. The hepatoduodenal ligament contains the portal triad; which consists of the bile duct, the hepatic artery proper, and the hepatic portal vein.
All right, let’s now have a look at the blood supply of the liver. It receives blood from two major sources; the hepatic portal vein, and the hepatic artery proper. The hepatic portal vein carries the majority of the blood that enters the liver.
It results from the merging of the splenic and superior mesenteric veins, which carry nutrient-rich blood from the gastrointestinal tract. This blood goes straight to the liver, specifically the hepatocytes, which are the liver cells that carry out tasks such as detoxification.
The remainder of the liver’s blood supply is oxygen-rich arterial blood from the hepatic artery proper, which stems from a branch of the celiac trunk called the common hepatic artery. This artery then bifurcates into the gastroduodenal artery and the hepatic artery proper, which then also bifurcates into the right and left hepatic arteries. The right and left hepatic arteries mainly supply the non-parenchymal part of the liver, such as the bile ducts within the liver.
Now, let’s talk about venous drainage of the liver. Within each hepatic lobule, blood flows from the periphery through sinusoids to a central vein. Blood from the central vein drains into a collecting vein, and then into one of three hepatic veins and finally to the inferior vena cava.
The right hepatic vein drains the right lobe of the liver, the left hepatic vein drains the left lobe, and the intermediate hepatic vein, which lies between these two lobes, drains the central part of the liver.
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