Week 4: Normal Liver Architecture

Question 1

What are the two representative functional units of the liver?

Answer 1

The hepatic Lobule or Hepatic Acinus

Question 2

What constitutes a Hepatic Lobule?

Answer 2

Hepatic lobule = efferent central vein with cords of hepatocytes radiating outwards towards multiple portal tracts.

Question 3

What constitutes a Hepatic Acinus?

Answer 3

Hepatic Acinus = Regular, 3D structure arranged around a portal tract containing a terminal portal vein (and its accompanying hepatic arteriole and bile ducts, etc.) from which blood flows into the acinar sinusoids (capillaries) before emptying into several hepatic venules at the periphery of the acinus.

The Hepatic Acinus is divided into three zones: Zone1, 2, & 3 - indicative of progressively decreasing tissue oxygenation

Question 4

What is a portal tract and what does it contain?

Answer 4

Most portal ducts contain:
Common Bile Duct
Several Bile Ductules
Hepatic Arteriole
Terminal Portal Vein
Lymphatic Channels
(sometimes a branch of vagus nerve)
Embedded in connective tissue
(smaller portal ducts are also surrounded on all sides by hepatocytes)

Question 5

Describe the normal arrangement of Hepatocytes in the Hepatic Lobule

Answer 5

Hepatocyte = polygonal epithelial cell with central, round nucleus

Hepatocytes are arranged in 1-cell-thick cords (in adults) and are separated by sinusoids, through which blood flows from the central terminal portal veins (of the portal tracts) to the terminal hepatic venules (arranged around the periphery of the hepatic acinus)

Question 6

Describe the histological composition of sinuoids in the liver

Answer 6

Specialised fenestrated endothelial cells and specialised macrophages (Kupffer cells)

Question 7

Main function of Hepatocytes? What is the name of the region of the hepatocyte in which this occurs?

Answer 7

Production of Bile

The bile canalicular membrane represents a specialised domain of the hepatocyte membrane for the purpose of bile formation. Bile canaliculi are not readily recognised macroscopically unless they are distended, such as in cholestasis

The bile canaliculi drain into the canals of Herring, then into bile ductules located at the periphery of the portal tract. In smaller portal tracts, the ductules join the interlobular bile ducts. Bile continues to drain into larger and larger bile ducts until it exits at the common hepatic duct.