The liver is a large essential organ found in the upper right quadrant of the abdomen. It is a multifunctional accessory to the gastrointestinal tract and performs such duties as detoxification, protein synthesis, biochemical production and nutrient storage to name but a few. It is the largest gland in the human body, weighing in at approximately 1.5 kilograms. It is completely covered by visceral peritoneum, with the exception of the bare area, which is where the liver is in contact with the diaphragm. This article will highlight the main anatomical knowledge that is generally required plus a few notes about the clinical pathology of the liver.
There are four anatomical lobes to the liver, which are further divided into even smaller segments in accordance with the blood supply. The right lobe is the largest of the four lobes and the left lobe is a flattened smaller one. The caudate lobe sits between the fissure for the ligamentum venosum and the inferior vena cava, while the quadrate lobe is located between the gallbladder and the fissure for the ligamentum teres hepatis. The left part of the liver which is known as the functional liver, contains all the lobes but the right.
The two major aspects or surfaces of the liver are the diaphragmatic surface and the visceral surface. The latter is shrouded by the peritoneum except at the porta hepatis and the bed of the gallbladder. It is directly related to several anatomical structures which include the duodenum, the gallbladder, the hepatic flexure, the transverse colon, the right kidney and suprarenal gland. The diaphragmatic surface is also covered by the peritoneum except in the bare area.
There are five ligaments that are directly related to the liver and they are called:
- the coronary ligament
- the left triangular ligament
- the falciform ligament
- the ligamentum teres hepatis
- the ligamentum venosum
The coronary ligament is formed by the peritoneal reflection from the diaphragm to the liver which has two layers that meet on the right.
The left triangular ligament is a mix of the falciform ligament and the lesser omentum.
The ligamentum teres hepatis is also known as the round ligament of the liver. It is a fibrous remnant of the umbilical vein which still extends from the internal aspect of the umbilicus up to the liver.
The ligamentum venosum is also an embryonic remnant of the ductus venosus. In utero it extended between the umbilical vein and the inferior vena cava.
Lastly, the falciform ligament which is not of embryological origin, but a peritoneal reflection of the upper abdominal wall from the umbilicus to the liver and has the round ligament of the liver on its free edge.
Porta Hepatis and Recesses of the Liver
The porta hepatis is the central intraperitoneal fissure of the liver that separates the caudate and the quadrate lobes. It is the entrance and the exit for several important vessels including the portal vein, the hepatic artery, the hepatic nervous plexus, the hepatic ducts and the lymphatic vessels.
The subphrenic recess which is split by the falciform ligament of the liver, is the divide between the liver and the diaphragm.
The hepatorenal recess is on the inferior right aspect of the liver and separates it from the kidney anterior inferiorly and the suprarenal gland posterior inferiorly.
Blood Supply and Lymphatic Drainage
The lymphatic drainage is governed mainly by the hepatic nodes which can be found around the porta hepatis. From there they continue to the celiac nodes and eventually drain into the cisterna chyli.
The liver is a special organ in the sense that it receives more venous blood than arterial blood and this is due to the fact that the liver helps clean the blood via detoxification. The majority of the vascular supply is brought into the organ by the portal vein and the rest from the hepatic artery. The hepatic veins drain the blood supply to the liver and they are formed by the union of the central veins which drain directly into the inferior vena cava just before it passes through the diaphragm.
The nervous supply of the liver comes from the hepatic plexus which travels along with the hepatic artery and the portal vein. The liver also receives sympathetic fibers from the celiac plexus and parasympathetic fibers from the anterior and posterior vagal trunks.
The characteristic clinical signs of severe hepatic dysfunction include jaundice and cholestasis, hypoalbuminemia, hyperammonemia, hypoglycemia, palmar erythema, spider angiomas, hypogonadism, gynecomastia, weight loss and muscle wasting. If one or more of the previously mentioned symptoms is present, a blood test is performed to test the liver’s hepatocyte integrity, biliary excretory function and hepatocyte function. The most common hepatic disorders include hepatic failure, cirrhosis, portal hypertension and cholestasis.