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Block 1: Physiology > Normal liver physiology > Flashcards

Normal liver physiology Flashcards

1
Q

What is the blood supply to the liver?

A 
Hepatic portal vein (SMV, IMV and Splenic Vein) 
Hepatic artery (from Coeliac Trunk)
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2
Q

What are the key functional zones of the liver?

A

Zone 1 - periportal hepatocytes (outermost and most oxygenated) - specialise in oxidative metabolism, gluconeogenesis and urea synthesis

Zone 3 - pericentral hepatocytes - specialise in drug metabolism, glycolysis and lipogenesis

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3
Q

What are sinusoids?

A

Vascular spaces running between plates of hepatocytes

Lined with epithelial cells

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4
Q

Are are the major cell types of the liver?

A

Hepatocytes
Cholangiocytes
Reticuloendothelial cell meshwork (made up of endothelial cells, Kupffer cells and lipocytes)

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5
Q

What is the function of cholangiocytes?

A

Line bile duct and secrete bicarbonate ions and water into the bile

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6
Q

What is the function of endothelial cells in the reticuloendothelial cell meshwork?

A

Line sinusoids

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7
Q

What is the function of Kupffer cells in the reticuloendothelial cell meshwork?

A

Immune cells anchored to the walls of sinusoids

Phagocytose bacteria and ingest inflammatory mediators

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8
Q

What is the function of lipocytes in the reticuloendothelial cell meshwork?

A

Found in space of Disse (between hepatocyte plate and sinusoid)
Storage of fat

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9
Q

What cells are affected in Cirrhosis?

A

Lipocytes - secrete collagen affecting structure of liver

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10
Q

What are the major functions of the liver?

A

DESPICES:

Drug metabolism and detoxification 
Energy metabolism and substrate interconversion 
Synthesis of plasma proteins 
Production of bile 
Immune functions 
Cholesterol processing 
Excretion of bilirubin 
Storage of vitamins and minerals
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11
Q

What molecules are metabolised for energy in the liver?

A

Carbohydrates (glycogenolysis, gluconeogenesis, glycogen synthesis, glycolysis)

Lipids (ketogenesis, triglyceride synthesis from fatty acids)

Proteins (deamination, urea formation)

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12
Q

What is the major plasma protein and its function?

A

Albumin
Able to carry various proteins and maintain osmotic pressure of plasma
Transports molecules in blood

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13
Q

What factors are synthesised in the liver for haemostasis and fibrinolysis?

A

Fibrinogen (for coagulation)
Alpha-1 antitripsin (coagulation inhibitor)
Plasminogen (fibrinolysis)

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14
Q

What carriage/ binding proteins are synthesised in the liver?

A

Transferrin (carries iron)
Sex hormone binding globulin
Thyroid-binding globulin

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15
Q

What are apolipoproteins?

A

Synthesised in liver

Bind lipids to form lipoproteins for transportation of lipids through lymphatic and circulatory systems

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16
Q

Where does cholesterol come from?

A

15% from diet

85% synthesised in body

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17
Q

What vitamins and minerals are stored in the liver?

A

Fat soluble vitamins: A, D, E, K

Minerals: Iron, Copper

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18
Q

How is bilirubin excreted?

A

Conjugated with glucoronic acid by hepatocytes to allow it to be exported into bile

19
Q

What is bilirubin?

A

Bile pigment formed from the breakdown of red blood cells into haem in the spleen and bone marrow

20
Q

Where is bile produced and stored?

A

Produced in liver

Stored in gallbladder (where water and salts are drawn out to increase concentration)

21
Q

How much bile is secreted per day?

A

0.7-1.2 litres

22
Q

What are the 6 major components of bile?

A
  1. Bile salts
  2. Lecithin
  3. Bicarbonate ions
  4. Cholesterol
  5. Bile pigments
  6. Trace metals
23
Q

What are the functions of bile salts?

A

Conjugated to taurine to increase solubility (become conjugated bile salts)
Exported down bile canaliculus to be excreted
Work to emulsify and digest fats in small intestine

24
Q

What is the fate of bile salts?

A

95% returned to liver via portal circulation

5% excreted in faeces

25
Q

What happens to the bile salts that are returned to the liver?

A

75% recycled as intact bile salts

25% deconjugated by bacteria in the terminal ileum and colon

26
Q

What forms the portal vein?

A

Superior mesenteric vein

Splenic vein

27
Q

What functions of the liver can malfunction in hepatobiliary diseases?

A
  1. Filter failure
  2. Elimination failure
  3. Metabolic failure
28
Q

How can filter failure manifest?

A

Portal hypertension (can cause bleeding)

29
Q

How can elimination failure manifest?

A

Jaundice (due to inability to remove bile)

30
Q

How can metabolic failure manifest?

A

Acidosis, muscle loss, coagulopathy, hepatorenal syndrome

31
Q

What occurs when there is a combination of filter, elimination and metabolic failure?

A

Encephalopathy

32
Q

What are some key signs of chronic liver disease?

A 
Clubbing 
Ascites
Spider Naevi 
Palmar erythema 
Dupuytren's contracture 
Gynaecomastia 
Jaundice
Oedema 
Splenomegaly
33
Q

What are the common causes of pancreatitis?

A

[I GET SMASHED]

Idiopathy
Gallstones
Ethanol 
Trauma 
Steroids
Mumps/ malignancy
Autoimmune
Scorpion bites
Hyperlipidemia, hypercalcaemia, hyperparathyroidism
ERCP
Drugs
34
Q

What are the common causes of liver injury?

A

Fat (non-alcohol fatty liver disease, non-alcohol steatohepatitis)
Alcohol
Virus
Iron

35
Q

What blood tests can be done to assess liver damage?

A

ALT/ AST (enzymes secreted by hepatocytes - elevated if damage)
Alk Phos/ yGT (test for bile duct damage - elevated if damage)

36
Q

What are ‘true’ tests of liver function?

A 
Prothrombin Time 
Bilirubin 
Albumin 
Urea/ Creatinine 
pH
37
Q

What imaging can be used to assess liver damage?

A

Ultrasound
CAT
MRI
Liver fibroscan (looks for elasticity of liver)

38
Q

What investigations are typically used to identify gallstones?

A

Ultrasound

No changes in blood test results

39
Q

What would raised bilirubin and Alk phos levels indicate?

A

Biliary obstruction

40
Q

What would differ in blood test results between acute and chronic pancreatitis?

A

Acute - raised amylase

Chronic - none

41
Q

How is cholesterol transported in the body?

A

Complex with lipoproteins

42
Q

What is the role of the liver in cholesterol processing?

A

Synthesises cholesterol from Acetyl CoA
Synthesises lipoproteins (used for cholesterol transport)
Exports cholesterol to body cells for synthesis of key products (e.g. steroid hormones)
Synthesis of bile salts
Extracts excess cholesterol from plasma
Exports excess cholesterol into bile for excretion in faeces

43
Q

How does cholesterol aid in bile salt formation?

A

Broken down into primary bile salts and conjugated with Taurine to form conjugated bile salts which enters bile canaliculus

44
Q

What hormones are involved in bile production and secretion?

A

Cholecystokinin (CCK) - secreted by the duodenum, stimulates secretion of bile (by stimulating contraction of gallbladder) and secretion of enzymes from the exocrine pancreas

Secretin - secreted by the duodenum (especially in response to acidity), stimulates production of bile in the liver and secretion of bicarbonate ions from the pancreas

Block 1: Physiology (15 decks)

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