Chapter 11 Discussion questions and answers

Discuss, with the aid of diagrams, the anatomical relationships between the liver, the gall bladder and the pancreas, and explain how pathological changes in one area can affect the other two.

Draw a diagram showing positions of the liver, gall bladder and pancreas (see Figure 11.3).
The gall bladder connects to the common hepatic duct via the cystic duct to form the common bile duct, which joins the pancreatic duct to form the Ampulla of Vater, which then drains into the duodenum.
The pancreatic duct , common bile duct and cystic duct are all small in diameter and can easily become blocked (eg by small gall stones), causing inflammation
Tumours of the gall bladder and pancreas can obstruct the common bile duct, resulting in blockage to bile secretion. Bile then accumulates in the liver and causes damage to the hepatic parenchyma.
Obstruction to blood flow in the liver, such as in right cardiac failure, also has potential to cause damage to hepatocytes.

Discuss the structural components of the liver

The liver is divided into two lobes and eight segments, each of which has its own branch of the blood supply and biliary drainage, and can therefore be surgically resected.
The liver has both an arterial and venous blood supply, bringing oxygen from the lungs and nutrients from the digestive tract.
Small bile ducts in the liver join and rejoin to form the biliary tree, which converges at the porta hepatis to form the common hepatic duct.
Portal vein, hepatic artery and common hepatic duct are closely aligned throughout the structure of the liver, down to microscopical level at the portal tracts.
The liver lobule is roughly hexagonal, with a portal tract at each exterior ‘corner’ and a central canaliculus.
Hepatocytes are organised in plates and are in contact with each other to form canaliculi into which bile is secreted, and face the sinusoidal space in which blood flows.
Liver acinus describes a triangular area of hepatocytes between a central vein and two portal tracts. This is important as it can be subdivided into zones radiating from the portal vein to the central vein, and is used to describe pathology.

Discuss how the ultrastructure of the hepatocyte is influenced by liver function

The membrane of the hepatocyte faces the sinusoid on the basolateral aspect, to facilitate exchanges of solutes within the blood, and the canaliculus on the apical aspect, to facilitate bile production.
Tight junctions separate the basolateral aspect of the hepatocyte from the apical aspect, sealing the canalicular space, which contains bile, from the intercellular space, the space of Disse and the sinusoidal lumen.
The space of Disse contains extracellular matrix which forms the reticulin fibres that support the cells.
Gap junctions and desmosomes contribute to exchanges between hepatocytes.
There is an abundance of mitochondria as there is a need for high ATP production.
Rough endoplasmic reticulin is prominent, with many ribosomes, and reflects the role of the liver in protein synthesis.
Smooth endoplasmic reticulum is involved in glucose and lipid metabolism as well as drug metabolism.
Hepatocytes are rich in glycogen, which can be seen as minute electron-dense particles scattered in the cytoplasm.