Accessory Organs - Liver Flashcards
Anatomical position?
Located in the right hypochondrium and epigastric areas. It also extends into the left hypochondrium.
Features of the liver surfaces?
There are two liver surfaces:
1) Diaphragmatic (anterosuperior) surface - smooth and convex and fits snugly under the curvature of the diaphragm. Note that the diaphragm that is in contact with the liver is not convered in visceral peritoneum.
2) Visceral (posteroinferior) surface - with the exception of the fossa of the gall bladder and the porta hepatis, it is covered in peritoneum. It is moulded by the shape of other organs, making it irregular and flat. It lies in contact with the right kidney, right adrenal gland, right colic flexure, transverse colon, 1st part of the duodenum, gallbladder, oesophagus, and the stomach.
What are the ligaments of the liver?
1) Falciform ligament - a sickle-shaped ligament that attaches to the anterior surface of the liver to the abdominal wall and forms a natural division between the right and left lobes of the liver. The free edge of this ligament contains the ligament teres, a remnant of the umbilical vein.
2) Coronary ligament (anterior and posterior folds) - attaches the superior surface of the liver to the diaphragm and demarcates the bare area of the liver. The anterior and posterior folds unite to become the triangular ligaments on the right and left lobes of the liver.
3) Triangular ligaments - formed by union of the anterior and posterior folds of the coronary ligament at the apex of the liver and attaches the left lobe of the liver to the diaphragm. Similarly, the right triangular ligament attaches the right liver lobe to the diaphragm.
4) Lesser omentum - attaches the liver to the lesser curvature of the stomach and the first part of the duodenum. It consists of the hepatoduodenal ligament (extends from the duodenum to the liver) and the hepatogastric ligament (extends from the stomach to the liver). The hepatoduodenal ligament surrounds the portal triad.
In addition, the liver is supported by the IVC by hepatic veins and supporting tissue.
What are the hepatic recesses relating to the liver?
These are anatomical spaces, which are of clinical importance as infection may collect in these areas, forming an abscess.
1) Subphrenic recess - located between the diaphragm and the anterior and superior aspects of the liver. They are divided into the right and left by the falcicform ligament.
2) Subhepatic recess - a subdivison of the supracolic compartment (above the transverse mesocolon), a peritoneal space located between the inferior surface of the liver and the transverse colon.
3) Morison’s pouch - a potential space of between the visceral surface of the liver and right kidney. This is the deepest part of the peritoneal cavity when supine, therefore pathological fluid such as ascites or blood is likely to accumulate in a bedridden patient.
Anatomical structure - macroscopic?
The liver is covered in a fibrous layer known as Glisson’s capsule.
It is divided into the right and left lobe by the falciform ligament. There are two further ‘accessory’ lobes that arise from the right lobe, and are located on the visceral surface of the liver:
1) Caudate lobe - located on the upper aspect of the visceral surface. It lies between the inferior vena cava and a fossa produced by the ligamentum teres.
2) Quadrate lobe - located on the lower aspect of the visceral surface. It lies between the gall bladder and the fossa produced by the ligamentum teres.
Separating the quadrate and the caudate lobe is the deep, transverse fissure, known as the porta hepatis. It transmits the vessels, nerves, ducts entering and leaving the liver with the exception of the hepatic veins.
Anatomical structure - microscopic?
The cells of the liver are known as hepatocytes are arranged into lobules. These are the structural units of the liver.
Each anatomical lobe is hexagonal in shape and is drained by a central vein. At the periphery of the hexagon are three structures known as the hepatic triad:
1) Arteriole - a branch of the hepatic artery entering the liver
2) Venule - a branch of the hepatic portal vein
3) Bile duct - a branch of the bile duct leaving the liver.
The portal triad contains lymphatic vessels and the vagus nerve fibres.
Vascular supply?
The liver has a dual blood supply:
1) Hepatic artery proper (25%) - supplies the non-parenchymal structures of the liver with arterial blood. It is derived from the coeliac trunk.
2) Hepatic portal vein (75%) - supplies the liver with partially deoxygenated blood, carrying nutrients absorbed from the small intestine. This is the dominant blood supply to the parenchyma, allowing the liver to perform its gut-related functions, such as detoxification.
Venous drainage - hepatic veins -> IVC
Nerve supply
The parenchyma of the liver is innervated by the hepatic plexus, which contains sympathetic (coeliac plexus) parasympathetic (vagus nerve) fibres. These fibres enter via the porta hepatis and follow the course of the hepatic artery and vein.
Glisson’s capsule is innervated by branches of the lower intercostal nerve - distension of the nerves result in a sharp localised pain.
Lymphatic drainage
Anterior aspect of the liver - hepatic lymph nodes, which drain into the colic lymph nodes and finally into the cisterna chyli.
Posterior aspect of the liver - phrenic and posterior mediastinal nodes, which drain into the right lymphatic and thoracic duct.
Clinical relevance: percutaneous liver biopsy
Used to obtain a liver tissue sample.
The biopsy is required in several clinical scenarios:
1) Abnormal LFTs of unknown cause
2) Liver malignancy
3) Hepatitis C - assessment of severity of liver fibrosis and disease progression.
4) Other liver conditions (hereditary haematochromatosis and autoimmune hepatitis)
5) Following liver transplantation
During the procedure, the liver is located via an ultrasound scan from a subcostal approach. Local and deep anaesthetic is injected where good liver tissue can be seen and the needle path is free of vessels. The patient is asked to hold their breath and biopsy is taken.
If a patient has abnormal clotting, (a relative contraindication), a percutaneous biopsy while platelets are running, or a transvenous biopsy can be attempted. This involves cannulating the internal jugular vein and passing the biopsy needle to the through to the hepatic veins to obtain a biopsy.
