Liver

Structure and Function

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Structure

The liver is soft and pliable and situated the upper part of the abdominal cavity, just below ‘t diaphragm. It is found just under the right hand side of the costal margin. The convex upper surface of the liver is moulded to the under surface of the domes of the diagram. The visceral surface is moulded to adjacent viscera and is therefore irregular in shape. The liver may be divided into a large right lobe and a small left lobe, divided by the falciform ligament of the peritoneum. The right lobe is divided into quadrate and caudate by the gall bladder, the fissure for the ligamentum venosum, the inferior vena cava and the ligamentum teres. The liver is completely surrounded by fibrous capsule which is partly covered by the peritoneum.

The lobes contain thousands of subunits called lobules. Each lobule has a central vein which is a tributary to the hepatic veins. There are portal canals in the spaces between lobes. These contains the portal triad:

• Branches of the portal vein
• Branches of the hepatic artery
• Tributaries of the bile duct

The porta hepatis or hilum of the liver is found on the posterioinferior surface and lies between the quadrate and caudate lobes. Attached to upper part of the lesser omentum it contains the:

• Hepatic Ducts (R+L)
• Hepatic Artery (R+L)
• Portal Vein
• Para + sympa nerve fibres
• Lymph nodes (drain liver and gallbladder into coeliac nodes)

Functions

Production and secretion of bile:

• Synthesizes heparin which is an anticoagulant
• Synthesises bile pigments from the haemoglobin of worn out rb corpuscles.
• Secretes bile salts

Carbohydrate metabolism:

• Gluconeogenesis (aminos, lactate or glycerol -> glucose)
• Glycogenolysis (glycogen -> glucose)
• Glycogenesis (glucose -> glycogen)

Lipid metabolism

• Cholesterol synthesis
• Production of triglycerides

Storage:

• Glycogen
• Vitamin B12
• Iron
• Copper

Other functions

• Breaks down haemoglobin (bile pigments are its metabolites), toxic stuff and some drugs. This sometimes results in toxication, where the metabolite is more toxic than its precursor.
• Converts Ammonia to urea.
• Production of coagulation factors
• In the first 3 months, the liver is the main site of RDC production in the foetus, but by the 42nd the bone marrow has completely taken over.

Lymph

Liver produce 1/3 to ½ of all body lymph. Lymph vessels in liver -> lymph nodes in porta hepatis -> celiac nodes.

Clinical conditions

Hepatitus viruses

Virus	Type of virus	Incubation Period	Illness	Carriers	Serological markers	Patient susceptibility	Transmission
HAV	ssRNA enterovirus	15-40 days	Mild; very low mortality	No	IgM anti-HAV antibody	Young	Faecal-oral
HBV	dsDNA hepadnavirus	50-180 days	Significant risk of chronicity and mortality	Yes	HBsAg, HBeAg	Any age	Blood and blood; needles; venereal.
HCV	Ss+RNA	40-55	Fluctuating; significant risk of chronicity and mortality	Yes	Anti-HCV antibody, HCV RNA	Any age	Blood and blood products; needles; possibly venereal.
HEV	ssRNA virus	30-50	No risk of chronicity; high mortality in pregnancy	No	Anti-HEV antibody	Any age	Faecal-oral

Hepatitis A

• Usually an epidemic.
• Virus excreted in faeces before the symptoms occur.
• Liver damage is direct cytopathic effect – rather than autoimmune.

Hepatitis B

• HBsAG – the Hep B surface antigen sticks to the liver cell surface, thus initiating an immune response, so the liver cell is attacked.
• HBeAG – prescence of this indicates liver disease.
• B goes chronic in 5% of patients

Hepatitis C

• High mutation rate. These ongoing changes in the virus make it difficult for the immune system to fight it off. For the same reason it is very difficult to develop a vaccine.
• Almost always blood born.
• It becomes chronic in 50-80% of cases, though when so is generally milder than chronic B.
• In chronic, cirrhosis occurs in 20-30%, though primary liver cancer appears to be much less common.