Liver

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Background
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The liver is the largest organ in the body weighing between 1200 and 1500 g in a healthy adult. It consists of
the following cells and structures:
• Hepatocytes
• Endothelial cells
• Ito cells
• Kupffer cells
• Central vein
• Portal tract
• And more!
Hepatocytes make up 80% of the volume of the liver and their primary function is to secrete bile. They are
specialised epithelial cells with 5 to 12 sides and are arranged in complex formations known as hepatic
laminae – basically plates of hepatocytes one cell thick. These laminae are bordered by hepatic sinusoids.
Grooves in the cell membranes provide spaces for the canaliculi. The hepatic sinusoids are low pressure
vascular channels lined with endothelial cells that receive blood from terminal branches of the hepatic artery
and portal vein at the periphery of lobules and deliver it into central veins.

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Figure 1. Image to show details of liver histology
Bile canaliculi are small ducts that collect bile produced by the hepatocytes. The canaliculi lead into the bile
ductules which in turn feed into the bile ducts. The bile ducts eventually merge into the right and left hepatic
ducts which unite and exit the liver as the common hepatic duct.
Figure 2. Image to show the anterior view of the liver

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The hepatic sinusoids are capillaries found between the rows of hepatocytes. They are highly permeable and
receive oxygenated blood from the hepatic artery and nutrient rich deoxygenated blood from the hepatic
portal vein.
Ito cells are hepatic stellate lipocytes (fat storing cells) that become activated in liver fibrosis due to
intoxication (i.e. have a role in hepatic cirrhosis) or hepatotoxic compounds such as carbon tetrachloride.
Their activation is associated with the expression of a sodium/calcium exchanger.
Kupffer cells are stellate reticuloendothelial cells located in the hepatic sinusoids. Their function is to destroy
old white and red blood cells, bacteria and foreign matter in venous blood from the GI tract.
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Functions of the liver
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The primary functions of the liver are:
Synthesis:
o Plasma protein synthesis (e.g. albumin)
o Synthesis of clotting factors, cholesterol, glucose
Storage
o Storage of glycogen
o Storage and metabolism of fats, carbohydrates, proteins
o Storage of fat soluble vitamins (A,D,E,K) and water soluble vitamin B12
Metabolism
o Detoxification of drugs and other toxins such as ammonia
o Metabolism of hormones (e.g. thyroxine to triiodothyronine, prednisone to prednisolone)
Immunological
o Role of kupffer cells in digesting and removing bacteria, fungi, old blood cells and other foreign
materials from blood

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Homeostasis
o Maintenance of normal levels of blood glucose
Production of bile
o Formation and secretion of bile (including bilirubin in bile)
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Liver disease
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Acute liver disease
If the onset of a patient’s symptoms occurred within the previous six months, then they are said to have acute
liver disease. Most cases of acute liver disease are self-limiting and consist of damage to or inflammation of
hepatocytes; they tend to resolve without long-term complications.
Chronic liver disease
Any patient whose symptoms persist for longer than six months is deemed to have chronic liver disease.
Typically there is longstanding hepatocyte damage resulting in permanent changes to liver structures.
Symptoms and signs of liver disease
Early symptoms of liver disease can include:
• Fatigue
• Loss of appetite
• Weight loss
• Abdominal pain
• Nausea
• Vomiting
• Diarrhoea
As the disease progresses symptoms evolve which are more serious in nature:
• Pruritis (caused by hyperbilirubinaemia)
• Jaundice (yellowing of skin and eyes)
• Bruising