Normal Liver Physiology

Question 1

Approximately what percentage of the cardiac output goes to the liver?

Answer 1

25%.

Question 2

The liver receives blood from which sources?

Answer 2

1. Venous flow from the hepatic portal vein.

2. Arterial flow from the hepatic artery.

Question 3

In the liver, hepatocytes are arranged in what structure?

Answer 3

Lobules

Question 4

In the liver, what is in the centre of each lobule?

Answer 4

A central vein.

Question 5

Describe venous blood flow through the liver starting at the portal vein.

Answer 5

1. Portal vein
2. Sinusoids
3. Central veins
4. Hepatic veins
5. IVC

Question 6

Name the zones of the liver lobules going from outer to inner.

Answer 6

Zone I
Zone II
Zone III

Question 7

In which zone of the liver lobules are hepatocytes most oxygenated?

Answer 7

Zone I.

Question 8

What is another name for the hepatocytes in Zone I?

Answer 8

Periportal.

Question 9

What is another name for the hepatocytes in Zone III?

Answer 9

Pericentral.

Question 10

What functions do the hepatocytes in Zone I specialise in?

Answer 10

1. Oxidative metabolism
2. Gluconeogenesis
3. Urea synthesis

Question 10

What functions do the hepatocytes in Zone III specialise in?

Answer 10

1. Drug metabolism
2. Glycolysis
3. Lipogenesis

Question 11

What structure does blood flow through in the lobules of the liver?

Answer 11

Sinusoids

Question 12

Which cells make up the walls of the sinusoids of the liver?

Answer 12

Sinusoidal endothelial cells.

Question 13

What is a Kupffer cell’s function?

Answer 13

Phagocytosis and defence of the liver against bacteria. They are also involved in the breakdown of red blood cells.

Question 14

What is the location of Kupffer cells?

Answer 14

In the sinusoids of the liver lobules.

Question 15

What is the location of the Lipocytes of the liver? What is this space called where they are found?

Answer 15

They lie between the hepatocytes and the sinusoids in what is called the Space of Disse.

Question 16

List 8 functions of the liver.

Answer 16

1. Production of bile
2. Cholesterol processing
3. Synthesis of plasma proteins
4. Energy metabolism and substrate interconversion
5. Drug metabolism and detoxification
6. Immune functions
7. Storage of vitamins and minerals
8. Excretion of bilirubin

Question 17

List the 6 major components of bile.

Answer 17

1. Bile salts
2. Lecithin (a phospholipid)
3. HCO3-
4. Cholesterol
5. Bile pigments
6. Trace metals

Question 18

What 4 things do hepatocytes secrete?

Answer 18

1. Bile salts
2. Cholesterol
3. Lecithin
4. Bile pigments

Question 19

What 2 things do cholangiocytes secrete?

Answer 19

1. Bicarbonate

2. Water

Question 20

What are bile acids?

Answer 20

Water-soluble derivates of cholesterol.

Question 21

What does conjugating bile acids with small molecules such as taurine and glycine do to them?

Answer 21

Makes them more soluble.

Question 22

What is Enterohepatic circulation?

Answer 22

The term enterohepatic circulation (EHC) denotes the movement of bile acid molecules from the liver to the small intestine and back to the liver.

Question 23

What percentage of bile salts are returned to the liver via the enterohepatic circulation? Of this percentage, what percentage are intact bile salts and deconjugated bile acids?

Answer 23

95%.

75% are intact bile salts, and 25% are deconjugated bile acids.

Question 24

Why would damage to the ileum, e.g. from Crohn's disease or ileal resection, result in steatorrhoea?

Answer 24

- It would impair the recycling of bile salts via enterohepatic circulation. - If the daily loss of bile salts exceeds the ability of the liver to synthesize new bile salts, the total circulating bile salt pool is diminished. - Bile salt deficiency leads to impaired fat digestion and absorption (via emulsion droplets and micelles). - Excess unabsorbed dietary fat is excreted in large, fatty and foul-smelling stools.

Question 25

The absorption of which vitamins is likely to be impaired with damage to the ileum?

Answer 25

Fat soluble vitamins - A,D,E, and K.

Question 26

What are the 4 main functions of bile salts?

Answer 26

1. Emulsification of dietary lipids, rendering them accessible to pancreatic lipases, and presenting fat digestion products for absorption. 2. Elimination of cholesterol. 3. Prevention of cholesterol precipitation in the gallbladder. 4. Facilitation of the absorption of fat-soluble vitamins.

Question 27

What percentage of cholesterol comes from diet and what percentage is synthesized by the body?

Answer 27

15% from diet | 85% synthesized - mostly in liver

Question 28

List 6 roles of the liver in cholesterol processing.

Answer 28

1. Synthesizes cholesterol from Acetyl-CoA. 2. Synthesizes lipoproteins, which transport cholesterol in plasma. 3. Exports cholesterol via circulation to body cells for synthesis of key products e.g. steroid hormones 4. Utilises cholesterol for the synthesis of bile salts. 5. Extracts excess cholesterol from plasma 6. Exports excess cholesterol in bile for excretion in faeces.

Question 29

How is bilirubin formed?

Answer 29

From the breakdown of haem in the spleen and bone marrow.

Question 30

How do hepatocytes make bilirubin into a water-soluble molecule?

Answer 30

Conjugate it with glucuronic acid.

Question 31

What are bile pigments?

Answer 31

Excretory products being disposed of by the liver via the gut.

Question 32

Once in the small intestine what happens to conjugated bilirubin? What does this form? What percentage of this substance is excreted in the faeces? What happens to the remainder?

Answer 32

The conjugated bilirubin is digested by bacteria to form Urobilinogen - 90% of the Urobilinogen is excreted in the faeces. The remainder re-enters circulation where a small portion is excreted by the kidney.

Question 33

Which cells are found in the Space of Disse?

Answer 33

Lipocytes

Question 34

What type of molecule is Lecithin?

Answer 34

A phospholipid.