Liver and Biliary System Diseases I

Question 1

Where is the liver located?

Answer 1

In the upper part of the abdomen, where it occupies the right hypochondriac and the greater part of the epigastric region. [Upper right quadrant, right below the diaphragm]

Question 2

The liver is divided into lobules by _________.

Answer 2

the line of insertion of the falciform ligament

Question 3

The right lobe has on its posterior-inferior surface, two smaller lobes called the _____ and ________.

Answer 3

caudate and quadrate lobes

Question 4

The liver is covered by ________.

Answer 4

the fibrous capsule of Glisson

Question 5

The gallbladder is connected to the GIT via the ________ and _______.

Answer 5

cystic duct and common bile duct.

Question 6

What is the function of the gallbladder?

Answer 6

To concentrate and store bile produced in the liver and release into the duodenum for the digestion of fats.

Question 7

How is bile released?

Answer 7

By muscular contraction of the gallbladder, primarily in response to gut hormones, especially cholecystokinin (CCK), that are stimulated by digestive products in the GIT.

Question 8

Describe the histology of the liver.

Answer 8

• Hepatocytes are arranged into hexagonal lobules, the functional units of the liver
• Each lobule has a hepatic venule (central vein) sitting in its centre and plates of hepatocytes separated by sinusoids into hepatic cords.
• At the edge of each lobule is a portal triad comprised of:
  i. Hepatic artery: supplies 25% of blood supply as arterial blood
  ii. Hepatic portal vein: supplies 75% of blood supply as deoxygenated nutrient-rich blood from GIT
  iii. Bile duct and lymph ducts

Question 9

What are the four types of cells that make up the liver?

Answer 9

1. Hepatocytes
2. Endothelial cells
3. Kupffer cells
4. Stellate/Ito cells

HEKS

Question 10

What are the functions of the hepatocytes?

Answer 10

They make up 80% of liver parenchyma. They:
- store glycogen, vitamin B12, folic acid and iron
- aid the turn over and transportation of lipids
- synthesis some plasma proteins e.g. albumin, prothrombin alpha and beta globulins and fibrinogen
- secrete bile to metabolise fat
- help in steroid hormone turnover and regulate cholesterol

Question 11

What is the function of the endothelial cells?

Answer 11

They line the sinusoids, which are capillaries that carry blood throughout the liver. Form fenestrations to control entry of plasma solutes and keep out RBCs

Question 12

What is the function of the stellate cells?

Answer 12

• They contain fat droplets which store vitamin A.
• Differentiate in myofibroblast-like cells and synthesise extracellular matrix
• Involved in liver regeneration

Question 13

What is the function of the kupffer cells?

Answer 13

• They are liver macrophages that adhere to lumen of sinusoids.
• Clear pathogens and act as APCs in adaptive immunity.
• Secrete cytokines and chemokines, which mediate inflammation.

Question 14

What are the functions of zones I and III of the liver?

Answer 14

Zone I - oxidative processes such as:
-gluconeogenesis
-beta-oxidation of fatty acids
-cholesterol synthesis
-amino acid metabolism
-ureagenesis
- bile formation

Zone III- these processes don’t require oxygen
-glycolysis
-lipogenesis
-ketogenesis
-xenobiotic metabolism (detoxification)
-glutamine formation

Question 15

What are the general functions of the liver?

Answer 15

1. Carbohydrate metabolism:
2. Protein metabolism:
3. Lipid metabolism:
4. Bile acid and Bilirubin metabolism:
5. Drug and hormone metabolism
6. Immunological function

Question 16

Highlight the carbohydrate metabolism function of the liver.

Answer 16

The liver regulates glucose via:
- Glycogenesis: storing glucose as glycogen
- Glycogenolysis: breaking down glycogen into glucose
- Gluconeogenesis: creating glucose from non-carbohydrate sources

Question 17

Highlight the protein metabolism function of the liver.

Answer 17

The liver regulates plasma protein levels.
- All circulating plasma protein except gamma-globulins are synthesised in the liver. - Synthesis of other proteins such clotting factors, complement proteins and acute phase proteins.
- Nitrogen excretion via amino acid transamination and oxidative deamination

Question 18

Highlight the lipid metabolism function of the liver.

Answer 18

• Storage of fatty acids as triglyceride within very low-density lipoproteins (VLDL)
• Beta-oxidation of fatty acids for energy
• Production of lipoproteins which transport insoluble fatty acids
• Cholesterol formation, redistribution and excretion

Question 19

Highlight the bile acid and bilirubin metabolism function of the liver.

Answer 19

• Synthesis of primary bile acids from cholesterol, which are then converted to secondary bile acids by GI microbiota
• Bile aids digestion of fats and provides alkaline pH for pancreatic ⁹ function
• Bilirubin, formed from RBC breakdown is conjugated with glucuronic acid in the liver and excreted within bile.

Question 20

Highlight the Drug and hormone metabolism function of the liver.

Answer 20

• Most xenobiotics are inactivated in the liver by CYP450 enzymes, and excreted in bile or urine after conjugation by hepatic transferases
• The liver ins involved in the catabolism of hormones such as insulin , glucocorticoids, GH and PTH
• Angiotensin is produced in the liver

Question 21

Highlight the immunological function of the liver.

Answer 21

• The liver helps filter the blood and remove debris, including bacteria and toxins
• Crucial site of gut-derived antigen presentation to Kupffer cells, NK cells and sinusoidal endothelium.
• The liver is involved in adaptive immunity via lymphocyte trafficking from the GIT.

Question 22

Where is bile secreted?

Answer 22

At the hepatocyte canicular membrane via bile transporter proteins, with the contribution of biliary ductular epithelium.

Question 23

Bile formation is stimulated by ______ and inhibited by _____.

Answer 23

Secretin and somatostatin

Question 24

What is enterohepatic circulation?

Answer 24

It is the process by which substances from the liver (e.g. bile acids) are secreted into the bile, absorbed by the small intestine are returned to the liver through the portal vein.

Question 25

Some of the bilirubin excreted in bile is broken down by bacteria into urobilinogen and undergoes enterohepatic circulation.
True or False?

Answer 25

True

Question 26

What are the methods of assessing liver function?

Answer 26

1. Blood tests (liver function tests)
2. Imaging
3. Endoscopy
4. Interventional radioscopy
5. Liver biopsy

BILIE

Question 27

Liver function tests are subdivided into:

Answer 27

i. Markers of liver injury
ii. Markers of liver synthesis

Question 28

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) release into serum indicate _______.

Answer 28

Hepatocellular damage, as these are enzymes predominantly located in hepatocytes.

Question 29

_______ and _______are chiefly found in biliary canaliculi and serum rises indicate intrahepatic cholestasis as well as extrahepatic bile duct damage or obstruction.

Answer 29

Alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (gamma-GT)

Question 30

Commonly measured indices of liver synthetic function are:

Answer 30

i. bilirubin
ii. albumin
iii. prothrombin time
iv. Coagulation factors - I, II, V, VII, IX, and X

Question 31

What are the different imaging methods used in liver function assessment?

Answer 31

i. Ultrasound scanning: detects liver lesions, gallbladder stones, biliary obstruction, portal hypertension and ascites. Fatty liver infiltration gives an echo ‘bright’ signal.
ii. Doppler: investigates blood flow and detects portal or hepatic venous occlusion
iii. CT scan and MRI: gives a clearer indication of liver size and architecture.

Question 32

Complications of portal hypertension such as oesophageal or gastric variceal bleeding can be detected using _____.

Answer 32

Endoscopy

Question 33

Hepatocellular enzyme induction and bile duct obstruction are indicated by __________.

Answer 33

Elevated ALP

Question 34

Decreased serum albumin indicates _________

Answer 34

Liver cirrhosis

Question 35

Elevated AST and ALT levels indicate:

Answer 35

• Hepatocellular injury (e.g. from alcohol)
• Drug induced hepatitis
• Hepatitis B and Hepatitis C

Question 36

AST-ALT ratio >2:1 indicates ___________.

Answer 36

Alcoholic liver disease