Liver Physiology

Question 1

Normal blood supply to the liver?

Answer 1

Oxygenated blood from the hepatic artery and deoxygenated blood from the hepatic portal vein

Aorta > Coeliac trunk > Hepatic artery proper > R&L hepatic arteries

Question 2

What makes up the portal triad?

Answer 2

Hepatic artery
Hepatic portal vein
Bile duct

Question 3

What’s the Pringle manoeuvre?

Answer 3

Pinch the free edge of the lesser momentum (containing portal triad) to cut off bloody supply during surgery

Question 4

Outline the organisation of the liver

Answer 4

Hepatocytes arranged in hexagonal lobules each with a portal triad

Within each lobule hepatocytes are arranged in plates, in a reticuloendothelial cell cage
Hepatocyte plates separated by sinusoids, draining blood into central veins, which converge to the hepatic vein

Question 5

Outline the functional zonation of liver lobules

Answer 5

Zone 1 (periportal) - most oxygenated so specialised in metabolism (oxidative metabolism, gluconeogenesis and urea synthesis)

Zone 3 (pericentral) - specialised for drug metabolism, glycolysis and lipogenesis

Question 6

What are the major cell types of the liver?

Answer 6

Hepatocytes = main functional units

Cholangiocytes = secrete HCO3- and H20 (line bile duct)

Reticuloendothelial cell cages lining hepatocyte plates are made of:
Endothelial cells
Kupffer cells (immune function)
Lipocytes (Stellate cells)

Question 7

What are the major functions of the liver?

Answer 7

Drug metabolism & detoxification
Energy metabolism & substrate interconversion
Synthesis of plasma proteins
Production of bile
Immune function
Cholesterol processing
Excretion of bile
Storage of vitamins & minerals

Question 8

What plasma proteins are produced by the liver?

Answer 8

Albumin
Fibrinogen and Plasminogen for haemostasis
Thyroid binding globulin, SHBG

Question 9

What are the 6 main components of bile and what is its function?

Answer 9

Aids digestion by neutralising acid and emulsifying lipids (it’s amphiphilic)

Bile salts
Lecithin (Phospholipid)
HCO3- and other salts
Cholesterol
Bile pigments
Trace metals

Question 10

What’s the role of the gallbladder with regards to bile production?

Answer 10

Liver produces bile which is stored and concentrated in the gallbladder

Absorbs H20 and salts to concentrate

CCK stimulates gallbladder to contract to release bile into duodenum via common bile duct

Question 11

What do hepatocytes and cholangiocytes secrete to form bile?

Answer 11

Hepatocytes:
Bile salts
Cholesterol
Bile pigments
Lecithin

Cholangiocytes:
HCO3-
H20

Question 12

Bile salts = (primary and secondary)

Answer 12

Primary bile salts = cholesterol + taurine

Secondary bile salts = cholesterol + glycine

Question 13

What’s the significance of the enterohepatic circulation?

Answer 13

Bile salts are released into the small intestine

95% of them will be recycled via the enterohepatic circulation and returned to the liver for reuse

5% will be excreted in faeces and will need to be replaced

Question 14

Of the 95% recycled primary bile salts, 75% are intact but 25% are deconjugated. Explain this

Answer 14

Some bile salts will be deconjugated in the terminal ileum by bacteria into primary bile acids and some are dehydroxylated into secondary bile acids

They then become deconjugated with taurine/glycine and process starts again

Question 15

What’s the function of bile salts?

Answer 15

Emulsify dietary lipids so they can be digested by pancreatic lipase

Elimination of cholesterol

Prevention of cholesterol precipitation in the gallbladder

Facilitates absorption of fat soluble vitamins

Question 16

What are the functions of cholesterol? (Lipid molecule)

Answer 16

Plasma membranes
Component of bile salts
Precursor for steroid hormones
Myelin

Question 17

Majority of cholesterol is synthesised in the liver, small amount from diet intake. What’s the role of the liver in cholesterol processing?

Answer 17

Synthesis from Acetyl CoA
Synthesises lipoproteins, which transport cholesterol in plasma
Exports plasma via circulation for synthesis of steroid hormones
Exports plasma to gallbladder for bile salts
Exports excess cholesterol for excretion in faeces
Extracts excess cholesterol from plasma

Question 18

What are fat soluble vitamins? That the liver stores

Answer 18

D
A
K
E
And minerals

Question 19

Outline the enterohepatic circulation

Answer 19

Circulation of bile acids, bilirubin, drugs from the liver to bile ending up in the small intestine and being absorbed across enterocytes to be transported back to the liver

Question 20

Outline the splanchnic circulation

Answer 20

Blood flow through the stomach, small intestine, large intestine, pancreas, spleen and liver

Portal vein carries blood draining from all of these organs

Question 21

What is ascites and how does it arise in cirrhosis?

Answer 21

Ascites = increased portal pressure and decreased plasma protein content causing transudation of fluid into extracellular space (abdominal cavity)

Decreased plasma Albumin by decreased synthetic function = decreased oncotic pressure of the blood = increased portal pressure

Question 22

Which metabolites cause hepatic encephalopathy?

Answer 22

Urea and ammonia build up in the blood by loss of urea cycle metabolism in the liver and get to the brain to cause mental confusion
= hallmark of liver failure

Question 23

What are two tests for synthetic liver function and why?

Answer 23

Albumin - decreased plasma albumin in liver failure due to impaired ability of liver to synthesise plasma proteins

Pro-thrombin time = increased/takes longer for blood to clot due to decreased synthesis of plasma proteins responsible for coagulation (fibrinogen/plasminogen)

Question 24

Which two liver function tests will be raised by hepatocyte damage and why?

Answer 24

Alanaine Transaminase and Aspartate Transaminase - they’re enzymes in hepatocytes so are released into bloodstream in hepatocyte damage

Question 25

Which two liver function tests will rise when there’s bile duct/obstructive liver damage?

Answer 25

Alkaline Phosphatase and Gamma GT - indicates bile ducts are blocked/inflamed

Question 26

Where is Alkaline Phosphotase found? Why is this important?

Answer 26

Bone and liver - raised levels may not definitively diagnose liver damage so should do other liver tests (bilirubin, GGT, ALT)