The Liver and Biliary System

Question 1

Where is the liver located and what is its structure?

Answer 1

Right upper quadrant in close association with other abdominal organs. 1/50th of your body weight. It is composed of two segments separated by the falciform ligament.
Blood leaves the liver via the left hepatic vein.
The liver appears shiny due to a protective connective tissue layer.

Question 2

Where is bile produced and what is its function?

Answer 2

Bile is produced by the gall bladder. It is secreted into the bile duct into the liver, which helps emulsify fat.

Question 3

The liver is divided into segments what does each segment contain?

Answer 3

A lobule/acinus - the functional part of the liver.

These are composed of: plates of hepatocytes, sinusoidal channels, inlet and exit blood vessels and bile canaliculi.

Question 4

Explain the livers blood supply

Answer 4

Portal vein - venous blood from gut (75%)
Hepatic artery - arteriole blood (25%)
25% of CO enters the liver = 1.3L/min
Blood enters, mixes in the sinusoids and drains via hepatic veins into the IVC near the right atrium.

Question 5

What is the liver stroma composed of

Answer 5

ECM materials - dynamic and complex macromolecules mainly collagens (I, II, III, IV, V and VI) produced by satellate cells.
Glycoproteins link cells to collagen/ECM
Integrins - for bidirectional communication between cells.

Question 6

Describe lobular organisation of the liver

Answer 6

The liver is organised into lobules around terminal branches of the hepatic vein. Between lobules are portal triads. Each triad consists of branches of a bile duct, portal vein and hepatic artery.

Question 7

What is fibrosis and cirrhosis?

Answer 7

Conditions where there is irreversible scaring of the liver which forms de to the livers fast regenerative process. Blood pressure will start to build up as it cannot diffuse through it as well. It also leads to disruption of lobular architecture.

Question 8

What cells are present in the liver?

Answer 8

Hepatocytes, epithelial cells, parenchymal cells, kupffer cells, satellate cells

Question 9

Describe the hepatocytes and their function in the liver

Answer 9

60-65% of liver tissue = most abundant
100 billion cells 
Polarised polyhedral epithelial cells
20-30M in size 
Function: glucose is taken up by the cells and is converted into glycol polysaccharides for storage. These cells do most of the liver functions. Hepatocytes produce bile.

Question 10

Describe biliary epithelium and their function in the liver

Answer 10

1-3% of liver tissue
Forms collecting vessels of increasing size to collect canalicular bile. Polarised cuboidal or columnar epithelial cells. Dense basement membrane to keep the bile in.

Question 11

Describe the liver endothelium and its function

Answer 11

Squamous epithelial cells, line the hepatic vasculature. They protect the parenchyma from blood cells, bacteria and viruses. Selective uptake of solutes and particles and selectively allow immune component eg. leukocytes have to bind to enter.

Question 12

Describe kupffer cells and their function in the liver

Answer 12

Kupffer cells are hepatic macrophages located within the sinusoids. Provide an immune response, they are 80% of all macrophages in the body.
Functions: phagocytosis, regulate microcirculation, removal of endotoxin.
Vey active receptor-mediated endocytosis. Can produce cytokines, present antigen and stimulate immune response.

Question 13

Describe stellate cells and their function in the liver

Answer 13

Also called Ito cells or lipocytes. 15% of non hepatocyte cells in the liver. Perisinusoidal fat/retinoid storing cells. Star shaped with multiple membrane processes and branching structure. Can transform to a more fibroblast like morphology in disease.
They store useful lipids.

Question 14

What is the function of the liver

Answer 14

Bile production
Detoxification of alcohol
Immune regulation
Production of clotting factor 
Production of glucose

Question 15

What is the digestive function of the liver?

Answer 15

Carbohydrate and fat metabolism. Storage of vitamins and minerals. Haemochromatosis is storing of iron.

Question 16

Why is cholesterol important?

Answer 16

Essential component of cell membranes- it establishes proper membrane permeability and fluidity.
An important component in the production of bile acids, steroid hormones and vitamin D.

Question 17

Production of bile and its function

Answer 17

The liver produces about 0.5L of bile a day by hepatocytes. The bile is recycled 6-8 times a day to recycle the bile salt which could run out otherwise. A few 100ml can be stored in the gall bladder and released into the intestine upon demand.
Bile is involved in the emulsification of fat in the intestine. Fat soluble vitamin uptake (A, D, E, K). Also used for excretion of some substances which cannot be cleared by the kidneys.

Question 18

Describe the immune function of the liver

Answer 18

Protection against pathogens is required as bacteria is often among the portal blood entering the liver. Kupffer cells are specialised phagocytic macrophages located in the liver, which engulf and digest these intestinal bacteria. Under the microscope kupffer cells appear black cells and an asymmetrical shape.

Question 19

Explain detoxification and elimination functions of the liver

Answer 19

Urinary excretion = solubilisation of compounds
Biliary excretion = lipophilic comounds
Drugs require a biotransformation:
Phase 1: Oxidation or reduction to make soluble (P450)
Phase 2: Conjugation to make water soluble
CYPs are the major enzymes involved in drug metabolism and deactivation - either directly or by facilitated excretion from the body.
Levels of P450 change as you age. Dosage needs to be more carefully monitored.

Question 20

What proteins are synthesised in the liver?

Answer 20

Albumin (50% of all plasma proteins), fibronectin, plasminogen, alpha-1 antitrypsin, transferrin, hepcidin.