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BRS - GI > Hepatobiliary System > Flashcards

Hepatobiliary System Flashcards

1
Q

What are the main parts of the liver (on the surface)?

A
  • right lobe
  • left lobe
  • caudate lobe
  • falciform ligaments
  • quadrate lobe
  • gall bladder
  • ligamentum teres
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2
Q

Where is the liver in the GI system?

A
  • anterior to gall bladder, duodenum, stomach , etc.
  • superior to the large intestine
  • in the right side of body
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3
Q

What is the hepatic portal system?

A

• connects capillaries of GI
tract with capillaries in liver
• nutrient-rich blood leaves GI tract + is first brought to liver for processing
before being sent to heart

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4
Q

What is the purpose of the hepatic portal vein?

A
  • 75% of blood supply inflow

* carries in venous blood drained from spleen, GI tract + associated organs

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5
Q

What is the purpose of the 3 hepatic veins?

A

• drains de-oxygentaed blood from liver into inferior vena cava

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6
Q

What is the purpose of the hepatic artery?

A
  • 25% of blood supply inflow

* carries in blood from aorta

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7
Q

How many functioning sections does the liver have?

A

8 : I-IV on left, V-VIII to right

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8
Q

What is a hepatic lobule?

A

• Hexagonal structural unit of liver tissue
• Each corner consists of a portal triad
• Links with 3x adjacent lobules
• Centre of liver lobule is a central vein - collects blood from hepatic sinusoids → hepatic veins → systemic
venous system
• Within lobule are rows of hepatocytes, each has sinusoid-facing side & bile
canaliculi-facing side

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9
Q

What is a hepatic acinus?

A
  • Functional unit of liver
  • Hard to define anatomically
  • Consists of two adjacent 1/6th hepatic lobules
  • Share 2x portal triads
  • Extend into hepatic lobules as far as central vein
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10
Q

What is a portal triad?

A

set of 3 vessels:
• branch of hepatic artery
• branch of hepatic vein
• branch of bile duct

• Branch of hepatic artery
• Brings O2-rich blood into
liver to support hepatocyte’s
high energy demands
• Branch of portal vein
• Mixed venous blood from
GIT (nutrients, bacteria &
toxins) and spleen (waste
products)
• Hepatocytes process
nutrients, detoxify blood &
excrete waste
• Bile produced by
hepatocytes drains into bile
canalicul
• Coalesce with
cholangiocyte-lined bile
ducts around lobule
perimeter
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11
Q

What is the function of the hepatic artery branch in the portal triad?

A

Brings O2-rich blood into
liver to support hepatocyte’s
high energy demands

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12
Q

What is the function of the hepatic vein branch in the portal triad?

A

Mixed venous blood from
GIT (nutrients, bacteria &
toxins) and spleen (waste
products) - Hepatocytes process nutrients, detoxify blood & excrete waste

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13
Q

What is the function of the bile duct branch in the portal triad?

A 
Bile produced by hepatocytes drains into bile
canaliculi - Coalesce with
cholangiocyte-lined bile
ducts around lobule
perimeter
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14
Q

How is blood moved in + out of the hepatic lobules?

A

• blood moves into hepatic
acinus via portal triad
• blood drains out of hepatic acinus via central vein

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15
Q

What is the 3-zone model?

A

Acinus split into 3 regions:
• Zone 1 (centre oval, high O2 + high toxin risk)
• Zone 2 (surrounds zone 1, medium O2 + medium toxin risk)
• Zone 3 (surrounds zone 2, lower O2 + lower toxin risk)

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16
Q

What zone of the acinus receives the earliest exposure to blood contents?

A

Zone 1

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17
Q

What is a sinusoidal endothelial cell?

A

• No basement membrane
• Fenestrated endothelium
• Allow lipids & large molecule movement to +
from hepatocytes

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18
Q

What is a Kuppfer cell?

A 
• Sinusoidal macrophages
• Attached to endothelial cell
• Phagocystosis
• Eliminate & detoxify
substances arriving in liver
from portal circulation
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19
Q

What is a hepatocyte?

A
  • 80% of liver mass
  • Cubical
  • Synthesis e.g. albumin, clotting factors & bile salts
  • Drug metabolism
  • Receive nutrients & building blocks from sinusoids
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20
Q

What is a hepatic stellate cell?

A
  • Exist in dormant state
  • Store vitamin A in liver cytosolic droplets
  • Activated (fibroblasts) in response to liver damage
  • Proliferate, chemotactic & deposit collagen in ECM
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21
Q

What is a cholangiocyte?

A

• Secrete HCO3- & H2O into bile

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22
Q

What are the functions of hepatocytes?

A

• Metabolic & catabolic functions: synthesis & utilisation of carbohydrates, lipids + proteins
• Secretory & excretory functions: synthesis
& secretion of proteins, bile + waste products
• Detoxification & immunological functions: breakdown of ingested
pathogens & processing of drugs

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23
Q

What is glycolysis?

A
  • anaerobic conversion of glucose → lactate (RBCs, renal medulla & skeletal muscle)
  • aerobic oxidation of glucose (CNS, heart, skeletal muscle, most organs)
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24
Q

What is glycogenesis?

A

synthesis of glycogen from glucose (liver & muscle)

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25
Q

What is glycogenolysis?

A

breakdown of glycogen to glucose

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26
Q

What is gluconeogensis?

A

production of glucose from non-sugar molecules

  • amino acids (glutamine) in liver & renal cortex
  • lactate (from anaerobic glycolysis in RBCs & muscles)
  • glycerol (from lipolysis)
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27
Q

What is lipolysis?

A

breakdown of triacylglycerols → glycerol & FFAs

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28
Q

What is lipogenesis?

A

synthesis of triacylglycerols

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29
Q

What are the 4 lobes of the liver?

A
  • right
  • left
  • caudate
  • quadrate
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30
Q

What lobe of the liver is the biggest?

A

right

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31
Q

What separates the right and left lobes?

A

middle hepatic vein

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32
Q

How are the 8 functioning sections supplied with blood?

A

each functioning segment has its own blood supply, etc.

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33
Q

Why is it important to know that the 8 functioning sections are supplied by blood vessels separately?

A

when doing a sectorectomy (removing part of the liver), only one of the blood vessels need to be tied off, not the whole artery

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34
Q

How do hepatocytes help with carbohydrate metabolism?

A
  • metabolises lactate from muscle cells to produce pyruvate
  • pyruvate is converted into glucose by gluconeogenesis
  • glucose is fed back into muscle cell for cell metabolism
35
Q

How do hepatocytes help with protein synthesis?

A

AAs from muscle cells or diet converted into secreted proteins e.g. plasma proteins, clotting factors, lipoproteins, etc.

36
Q

How do hepatocytes help with synthesis of non-essential AAs?

A

gg

37
Q

What is the problem that muscle cells have with utilising AAs to produce glucose?

A
  • converting pyruvate to glucose requires energy

* removing nitrogen as urea requires energy

38
Q

What is the solution to the muscle cells’ problem w utilising AAs?

A

let liver deal with it in the glucose - alanine cycle

39
Q

How do hepatocytes help with deamination + protein metabolism?

A

g

40
Q

How do hepatocytes help with triglyceride metabolism?

A

g

41
Q

How do hepatocytes help with lipoprotein synthesis?

A

g

42
Q

How do hepatocytes help with storage?

A

• Stores fat soluble vitamins (A,D,E,K) sufficient for 6-12 months (except Vitamin K where store is
small)
• stores iron as ferritin so it is available for erythropoiesis

43
Q

How do hepatocytes help with detoxification (xenobiotics)?

A

P450 enzymes
• Phase 1 (modification) = more hydrophilic
• Phase 2 (conjugation) = attach water soluble side chain to make less reactive

44
Q

What is bile?

A

g

45
Q

What are the uses of bile?

A
  • Cholesterol homeostasis
  • Absorption of lipids & lipid soluble vitamins (A, D, E, & K)
  • Excretion of xenobiotics/drugs, cholesterol metabolites, adrenocortical & other steroid hormones, alkaline phosphatase
46
Q

How much bile is produced everyday?

A

500 ml

47
Q

What colour is bile?

A
  • yellow = pigment bilirubin

* green = pigment biliverdin

48
Q

What two cells secrete bile? In what proportions?

A
  • hepatocytes = 60% of bile

* cholangiocytes = 40%

49
Q

What happens in primary secretion?

A
  • Bile secretions reflect serum concentrations

* Secretion of bile salts (acids), lipids & organic ions

50
Q

What happens in secondary modification?

A

• Alteration of pH (alkaline electrolyte solution)
• H2O drawn into bile by osmosis via paracellular junctions
• Luminal glucose & organic acids reabsorbed
• HCO3- & Cl- actively secreted into bile by
CFTR (Cystic Fibrosis Transmembrane
Regulator)
• IgA exocytosed

51
Q

How is biliary excretion of bile salts + toxins carried out?

A

performed by biliary transporters on apical surface of hapatocytes + cholangiocytes

52
Q

What are the main transporters of bile salts + toxins?

A
  • Bile Salt Excretory Pump (BSEP) – active transport of BAs into bile
  • MDR related proteins (MRP1 & MRP3)
  • Products of the familial intrahepatic cholestasis gene (FIC1)
  • Products of multidrug resistance genes: MDR1 → excretion of xenobiotics & cytotoxins
53
Q

What are bile salts synthesised from?

A

cholesterol

54
Q

How does the liver modify bile salts?

A

Na+ and K+ salts of bile acids are conjugated in liver to glycine + taurine

55
Q

How does gut bacteria affect bile acids?

A

converts primary bile acids from the liver to secondary bile acids

56
Q

What is the function of bile salts?

A
  • Reduce surface tension of fats

* Emulsify fat prior to its digestion & absorption

57
Q

What are the two primary bile acids?

A
  • cholic acid

* chenodeoxycholic acid

58
Q

What does cholic acid get converted into?

A

deoxycholic acid

59
Q

What does chenodeoxycholic acid get converted into?

A

lithocolic acid

60
Q

What do bile salts form?

A

micelles

61
Q

What are the features of micelles?

A
  • Steroid nucleus planar - has 2 faces (amphipathic)
  • 1 surface hydrophilic domains (hydroxyl & carboxyl) faces out, dissolves in water
  • 2nd surface hydrophobic domains (nucleus & methyl) faces in, dissolves in fat
  • Free fatty acids & cholesterol INSIDE
62
Q

How is bile flow + secretion regulated between meals?

A

sphincter of oddi closed + bile diverted into gall bladder for storage

63
Q

How is bile flow + secretion regulated when eating?

A

sphincter of oddi relaxes

64
Q

How is increase in bile mediated?

A
  • gastric contents enter duodenum causing release of cholecystikinin (CKK)
  • CCK causes gall bladder to contract = increase in bile
65
Q

What is the enterohepatic circulation?

A

g

66
Q

What happens to 95% of bile salts in the enterohepatic circulation?

A

absorbed by the terminal ileum by the Na+/bile salt co-transport Na+ / K+ ATPase system

67
Q

What happens to 5% of bile salts in the enterohepatic circulation?

A

converted to secondary bile acids in colon:
• deocycholic acid is absorbed
• 99& of lithocolic acid excreted in stool

68
Q

What happens to absorbed bile salts?

A

absorbed bile salts go back to the liver + re-excreted in bile

69
Q

What are the functions of the gall bladder?

A

stores + concentrates + acidifies bile

70
Q

How is gall bladder contraction triggered by CKK?

A

binds to CCKA receptors & neuronal plexus of GB wall (innervated by preganglionic parasympathetic fibres of vagus nerve)

71
Q

What is bilirubin?

A

water insoluble yellow pigment

72
Q

What happens to bilirubin in the liver?

A
  • dissociates in the liver + enters hepatocytes

* bilirubin combined w/ 2 molecules of UDP-glucuronate = bilirubin diglucuronide (direct bilirubin)

73
Q

What are the 3 sources of bilirubin?

A
  • 75% from Hb (erythrocytes) breakdown
  • 22% from catabolism of other haemoproteins
  • 3% from ineffective bone marrow erythropoiesis
74
Q

How much bilirubin is excreted into bile everyday?

A

200-250mg

75
Q

How is bilirubin processed?

A
  • 85% excreted in faeces
  • 15% enters enterohepatic circulation
  • 1% enters systemic circulation & excreted by kidneys
76
Q

How is bilirubin excreted in faeces?

A

bilirubin → urobilinogen → stercobilinogen → stercobilin (brown compound)

77
Q

How is bilirubin processed in enterohepatic circulation?

A
  • Bilirubin → deconjugated → lipophilic form
  • Urobilinogen
  • Stercobilinogen
78
Q

What is jaundice?

A
  • medical condition w/ yellowing of the skin or eyes, arising from excess of pigment bilirubin
  • typically caused by obstruction of bile duct, by liver disease, or by excessive breakdown of RBCs
79
Q

What are normal levels of bilirubin?

A

• normal = < 17 µmol/L and • not normal = > 34-51 µmol/L

80
Q

What are the two types of high bilirubin?

A
  • unconjugated (indirect)

* conjugated (direct)

81
Q

How do you confirm conjugated bilirubin?

A

by finding bilirubin in the urine

82
Q

What are causes of jaundice?

A
  • acute inflammation of the liver
  • inflammation of bile duct
  • obstruction of bile duct
  • haemolytic anaemia
  • gilbert’s syndrome
  • cholestasis
  • Crigler-Najjar syndrome
  • Dubin-Johnson syndrome
  • Pseudojaundice
83
Q

What is ERCP?

A
  • endoscopic retrograde cholangiopancreatography
  • combines use of endoscopy + fluoroscopy to diagnose + treat certain problems of the biliary or pancreatic ductal systems
84
Q

What is percutaneous transhepatic cholangiogrpahy? (PTC)

A

Radiological technique used to visualise the anatomy of the biliary tract

BRS - GI (3 decks)

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