secretion and excretion (lecture series)

Question 1

What are the functions of the liver ?

Answer 1

• storage of carbs, lipids and vitamins
• synthesis of glucose, ketone bodies, amino acids, cholesterol, fatty acids
• phagocytosis of particulates (performed by kupffer cells)
• degradation of endogenous compounds (ammonium, drugs, toxins)
• manufacture plasma proteins
• activation/inactivation of hormones
• excretion of lipophilic waste products
• secretion of emulsifiers (bile salts)

Question 2

What is the blood supply to the liver ?

Answer 2

• 75% portal vein
• 25% hepatic artery

Question 3

What is blood like that comes to the liver from the portal vein ?

Answer 3

• rich in absorbed nutrients
• contains recycled bile acids/salts

Question 4

What is the hepatic artery a branch of ?

Answer 4

celiac artery

Question 5

How much blood-per-min enters the liver via the portal vein ?

Answer 5

1300 ml/min

Question 6

How much blood-per-min enters the liver via the hepatic artery ?

Answer 6

500 ml/min

Question 7

Where does blood empty into once in the liver, regardless which vessel it came through ?

Answer 7

hepatic sinusoids

Question 8

Where do hepatic sinusoids run?

Answer 8

through layers of hepatocytes

Question 9

Where does blood from hepatic sinusoids drain into ?

Answer 9

hepatic veins, back to vena cava

Question 10

How many zones of the liver are there between the portal vein/hepatic artery and the central vein ?

Answer 10

3

Question 11

What are the 3 zones of the liver that are based upon oxygen supply ?

Answer 11

1. periportal (closest to portal vein/hepatic artery)
2. intermediary
3. pericentral/perivenous/centrilobular (closest to central vein)

Question 12

Which of the 3 liver zones contains the most oxygen rich blood ?

Answer 12

periportal zone (closest to portal vein/hepatic artery)

Question 13

What processes occur in the periportal zone of the liver ?

Answer 13

• amino acid catabolism
• gluconeogenesis
• cholesterol synthesis

Question 14

What processes occur in the pericentral zone of the liver ?

Answer 14

• lipid synthesis
• ketogenesis
• glutamine synthesis
• drug metabolism

Question 15

In which zone of the liver does drug metabolism occur ?

Answer 15

pericentral (closest to central vein)

Question 16

In which zone of the liver would you first see fibrosis occurring due to liver disease ?

Answer 16

**pericentral zone ** (around base of central vein)

Question 17

Does bile move through the liver in the same or opposite direction to blood ?

Answer 17

opposite direction towards the bile ducts next to the portal vein/hepatic artery

Question 18

Are the bile ducts located next to
a) portal vein/hepatic artery ?
b) central vein?

Answer 18

portal vein/hepatic artery

Question 19

What are hepatocytes ?

Answer 19

polarised epithelial cells in the liver

Question 20

What are the epithelial cells of the hepatic sinusoids like ?

Answer 20

fenestrated = small holes in them

Question 21

What does ‘fenestrated epithelium’ mean ?

Answer 21

epithelium has small holes in it, which allows large substances to pass through

Question 22

What is the basolateral membrane of hepatocytes closest to …
a) hepatic sinusoid ?
b) bile canaliculus ?

Answer 22

hepatic sinusoid

Question 23

What is the apical membrane of hepatocytes closest to …
a) hepatic sinusoid ?
b) bile canaliculus ?

Answer 23

bile canaliculus

Question 24

What is another name for the basolateral membrane of a hepatocyte ?

Answer 24

sinusoidal membrane

Question 25

What is another name for the apical membrane of a hepatocyte ?

Answer 25

canalicular membrane

Question 26

What are the functions of bile ?

Answer 26

• secretion of bike salts/acids to aid intestinal lipid digestion and absorption
• ** secretion of water** and electrolytes
• excretion of waste products (those that aren’t easily excreted by the kidney)
• excretion of hormones
• excretion of drugs and other xenobiotics

Question 27

How much bile is produced/secreted by liver each day ?

Answer 27

1000 ml/day

Question 28

How much of the total secreted bike reaches the duodenum ?

Answer 28

half = 500 ml/day

Question 29

Where is bile stored between meals ?

Answer 29

the gall bladder

Question 30

What does the gall bladder do to bile between meals ?

Answer 30

concentrates it / decreases its volume

Question 31

What does bile contain ?

Answer 31

• bile salts/acids
• phospholipids
• cholesterol
• bilirubin (conjugated)
• metabolises of hormones/drugs
• heavy metal ions
• electrolytes (water + bicarbonate)

Question 32

What is the difference between bile salts and bile acids ?

Answer 32

bile salts = conjugated bile acids

Question 33

Which transport proteins excrete bile salts into bile canalicoli ?

Answer 33

• BSEP (bile salt export pump) main
• MRP2 (multidrug resistance-associated protein 2)

both part of the ABC transporter family

Question 34

What does ‘ABC transporters’ stand for ?

Answer 34

ATP-Binding cassette transporters

Question 35

Give an example of an ABC-A transporter ?

Answer 35

ABCA1 = cholesterol transporter

Question 36

Give an example of an ABC-B transporter ?

Answer 36

BSEP (bile salt transporter)

Question 37

Give an example of an ABC-C transporter ?

Answer 37

MRP2 (bile salt transporter)

CFTR
SUR1

Question 38

What do ABC transporters use in order to function ?

Answer 38

ATP

Question 39

What are the 4 classes of ABC transporters ?

Answer 39

• ABC-A
• ABC-B
• ABC-C
• ABC-G