Physiology - hepatobiliary

Question 1

Major types of cells in the liver

Answer 1

Hepatocytes (majority)

Kupffer cells

Hepatic stellate cells

Liver sinusoidal endothelial cells

Cholangiocytes

Question 2

Function of hepatocytes

Answer 2

1. Metabolism
   
   • synthesise glucose
   • store glycogen
2. Protein synthesis
3. Detoxification
4. Bile production
5. Drug metabolism

Question 3

Function of Kupffer cells

Answer 3

Phagocytosis
remove pathogens, dead cells, debris

# liver macrophages

Question 4

Function of hepatic stellate cells

Answer 4

Storage of iron & vitamins A, D, E, K

Question 5

What is bile?

Answer 5

yellowish-green fluid produced by the liver and stored in the gallbladder

• released in the duodenum to emulsify fats

Question 6

Composition of bile

Answer 6

• water
• bile salts
• bilirubin
• cholesterol
• phospholipids
• electrolytes

Question 7

Function of bile

Answer 7

1. Aids fat digestion
2. Excretes wastes (bilirubin, drugs)
3. Neutralises stomach acid

Question 8

What is the biliary system?

Answer 8

A network of organs & ducts involved in the production, storage, and transport of bile

Key components:
Liver - bile production
Gallbladder - bile storage
Bile duct - transport bile to small intestine

Question 9

What is the common hepatic duct?

Answer 9

Tube that carries bile from the liver

• right & left hepatic ducts join to form common hepatic duct

Question 10

Common bile duct is formed by …..

Answer 10

the union of common hepatic duct (from liver) and cystic duct (from gallbladder)

Question 11

What controls biliary secretion?

Answer 11

Hormones (cholecystokinin, secretin)

Bile salts

Vagus nerve

• stimulated in response to fatty chyme

Question 12

How does cholecystokinin (CCK) promote bile secretion?

Answer 12

CCK stimulates:

• gallbladder to contract, releasing bile through cystic duct into common bile duct
• sphincter of Oddi to relax, allowing bile to enter duodenum

Question 13

How does secretin promote bile secretion?

Answer 13

Stimulates bile ductular cells to secrete bicarbonate & water secretion, in response to presence of acid in duodenum

• this increases volume of bile entering duodenum, hence increases bile flow

Question 14

What is the enterohepatic circulation?

Answer 14

• when substances metabolised in the liver are excreted through bile (into duodenum)
• then reabsorbed into bloodstream through ileum, returning to the portal blood (liver)
• from liver → bile → recycled

Question 15

What is detoxification in liver?

Answer 15

conversion of potentially harmful substances into less toxic, easily excretable forms

Question 16

Phases of detoxification

Answer 16

Phase I : Metabolism
- cytochrome P450 modify toxins
(oxidise, reduce, hydrolyse them)

Phase II : Conjugation
- enzymes convert phase I byproducts into water-soluble form for elimination through urine or bile

Phase III : Elimination
- transport out of hepatocyte into canaliculi

Question 17

What are biliary transporters?

Answer 17

Membrane proteins that facilitate movement of various substances across membranes of hepatocytes and cholangiocytes

• cholangiocytes are cells lining bile ducts

Question 18

Examples of biliary transporters

Answer 18

1. Bile salt export pump (BSEP)
   
   • bile salts from hepatocytes into bile canaliculi
2. Multidrug resistance protein 2 (MRP2)

Question 19

What is bilirubin?

Answer 19

• component of bile

Bilirubin is produced when old red blood cells are broken down.

Is normally excreted from the body.