Liver

Question 1

Name the Liver’s Exocrine (Digestive) functions:

Answer 1

Bile salts for digestion & absorption of fats, & bicarbonate rich to neutralize acid in duodenum.

Question 2

What are the Liver’s Endocrine functions:

Answer 2

Hormone secretion e.g. insulin like growth factor

Question 3

What does the Liver metabolise?

Answer 3

Carbohydrates, proteins & fats

Question 4

What does the Liver synthesize cholesterol into?

Answer 4

Converts cholesterol into bile.

Question 5

What are examples of Excretion & Degradation in the Liver?

Answer 5

e.g. Secretes bile pigments into bile, destroys red blood cells

Question 6

What are the four Lobes of the Liver?

Answer 6

Left, Right, Caudate (next to inferior vena cava) & Quadrate (next to gall bladder).

Question 7

What is the Diaphragmatic Liver surface?

Answer 7

Superior upper surface of the liver.

Question 8

What is the visceral Liver surface?

Answer 8

Faces downwards (abdominal organs), has the porta hepatis & gallbladder.

Question 9

What does the Falciform ligament do?

Answer 9

Separates right & left Liver lobes, & attaches the Liver to the diaphragm & abdominal wall

Question 10

What are the two sources of blood going to the liver?

Answer 10

Nutrient rich blood from the GI tract via the hepatic portal vein, & oxygen rich blood from the hepatic artery from the heart.

Question 11

Describe the passage of nutrient rich blood from the intestines to the heart.

Answer 11

Nutrient rich, oxygen deficient blood from the intestines to hepatic portal vein to liver, mixing with oxygenated blood from the hepatic artery, into the hepatic vein into the inferior vena cava to the heart, which goes out the aorta to the hepatic artery, back to the liver.

Question 12

Describe the passage of blood in the liver ultrastructure:

Answer 12

Blood flows in from the hepatic portal vein & hepatic artery in the portal triads into the liver, flowing through the hepatic lobule via sinusoidal vessels into the central vein, where it empties into the hepatic veins, then the inferior vena cava, before reaching the heart.

Question 13

Describe the movement of bile in the Liver towards the Gall Bladder:

Answer 13

Bile flows the opposite direction of blood through the liver lobule, down the bile canaliculi towards the portal triad, flowing into the bile ductules, then towards the GI tract & gall bladder.

Question 14

Define Hepatocytes:

Answer 14

Specialized polarized cells (asymmetrical cell structure) which separate sinusoidal blood from the canalicular bile.

Question 15

Directions each face:
1) Basolateral Membrane:
2) Apical Membrane:

Answer 15

1) faces the liver sinusoidal endothelial cells
2) faces the bile canaliculi jointly with the directly opposing hepatocytes

Question 16

What does the Bile contain?

Answer 16

Liver product, containing HCO3-, cholesterol, lecithin (a phospholipid), bile pigments & salts
(Bile salts are for the absorption of water insoluble fats).

Question 17

Liver lobule:

Answer 17

Counter current flow of blood & bile.
Bile ducts lined by hepatocytes.
Blood sinusoid lined by single layer of fenestrated endothelial cells.
Portal triad composed of portal hepatic vein, portal artery & bile duct.
Central vein drains into the vena cava.

Question 18

What’s the purpose of Fenestrated sinusoidal endothelial cells?

Answer 18

• Filter between the lumen of the hepatic sinusoid & hepatocytes.
• Minimize any barrier for the bi-directional transfer of small or soluble substrates between blood & the extracellular space of Disse.

Question 19

Define: Kupffer cells

Answer 19

Macrophages inside the lumen of the sinusoids of the liver, adherent to endothelial cells.
Senses & uptakes pathogens & removes activated host cells

Question 20

Define: Stellate cells

Answer 20

Thought to be involved in liver fibrosis.

Question 21

Describe: Bile duct circulation

Answer 21

• Bile is transported down bile canaliculi in the liver which empties into bile ductules & then bile ducts, then empties into the hepatic ducts.
  Bile then enters the duodenum or diverted to the cystic duct into the gall bladder.

Question 22

Describe the uses of Cholesterol:

Answer 22

Synthesis of cell membranes, contributes to membrane fluidity & precursor for the synthesis of several molecules

Question 23

Describe: Cholesterol synthesis

Answer 23

1) Acetyl CoA is converted to Mevalonate, which is then converted to isopentenyl pyrophosphate, which is synthesized into Squalene, which undergoes cyclization into lanosterol, which undergoes through several steps to eventually form cholesterol.

Question 24

Describe how cholesterol is transported:

Answer 24

Cholesterol is lipophilic & doesn’t dissolve well in (aq) environment, so it’s packaged with phospholipids & apolipoproteins to form lipoproteins.
Lipoproteins’ outer surface are hydrophilic phospholipids, allowing it to more easily dissolve in (aq) environments.

Question 25

How is Bile produced?

Answer 25

*Hepatocytes secrete hepatic bile (contains bile salts, bile pigments, cholesterol & lecithin) into the bile canaliculi.
*Epithelial cells lining the bile ducts secrete a HCO3- rich fluid that increase the volume of the bile.

Question 26

Difference in formation of primary & secondary bile acids?

Answer 26

*Primary Bile acids - synthesized from cholesterol & released into the intestine upon hormone stimulation
*Secondary bile acids - formed in the intestine by the action of bacteria flora.

Question 27

Purpose of Bile salts?

Answer 27

hydrophobic & hydrophilic regions that aggregate to form micelles at a C.M.C. Important for the emulsification of fats

Question 28

Purpose of Bile acids?

Answer 28

• Primary/secondary bile acids are conjugated to amino acids to generate water soluble bile salts.

Question 29

Define & Describe: Enterohepatic circulation

Answer 29

• 95% bile salts enter intestine are recycled back to the liver via portal vein at the ileum
• 5% are lost in faeces (liver replaces)
• Uptake of bile salts from portal blood into hepatocytes occurs via active transport pathway.
• Can cause Enterohepatic recycling, where drugs may reach the liver again.

Question 30

Describe: The Sphincter of Oddi

Answer 30

a ring of smooth muscle where the common bile enters the small intestine. When closed directs bile to the gall bladder.

Question 31

Cholecystokinin (CCK):

Answer 31

When fatty acids enter the duodenum, CCK is released, resulting in gallbladder releasing bile into the duodenum & the Sphincter of Oddi relaxing.

Question 32

Describe: Gall Bladder

Answer 32

Stores bile not required immediately for digestion of meals, concentrating bile by removal of salts & water

Question 33

Describe: IGF 1 & 2

Answer 33

• Synthesized in Liver, potent growth promoting effects.
• IGF-1 levels low in infancy, peak in puberty during growth & declines in adult
• IGF-2 important in foetal & neonatal growth

Question 34

Describe: P450 Enzymes

Answer 34

superfamily of related enzymes responsible for Phase 1 reactions. Variation in these enzymes may alter therapeutics, & naturally occurring substances can inhibit (e.g. grapefruit juice) or induce (brussels sprouts) P450 enzymes, impacting drug metabolism

Question 35

Describe: Phase 1 & 2 of drug metabolism

Answer 35

Phase 1 - Oxidation, hydroxylation, dealkylation, deamination, hydrolysis
Phase 2 - conjugation step to less active or more lipid soluble product.