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Gastroenterology > Hepatobiliary system > Flashcards

Hepatobiliary system Flashcards

(48 cards)

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1
Q

Describe the blood supply to the liver?

A

Hepatic artery 25%

Portal vein 75%

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2
Q

Describe the outflow from the liver?

A

Bile through bile duct

3 Hepatic vein to inferior vena cava to heart

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3
Q

What is the purpose of the blood delivered to the liver by the portal vein?

A

?

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4
Q

What is the purpose of the blood delivered to the liver by the portal vein?

A

? check rexording

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5
Q

What is the structural unit of the liver?

A

Hepatic lobule In a hexagonal shape

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6
Q

What links 3 adjacent lobules?

A

Portal triad

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7
Q

What is in the centre of the liver lobule?

A

Central vein which collects blood from the hepatic sinusoids –> hepatic veins –> systemic venous system

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8
Q

What is within the lobule?

A

Rows of hepatocytes
Each with a sinuosoid-facing side
And a bile canaliculi facing side

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9
Q

What is found within the portal triad?

A

Branch of hepatic artery
Branch of portal vein
Bile duct

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10
Q

What does the bile duct do which is brought to lobules by portal triad?

A

Bile produced by hepatocytes drains into bile canaliculi

Coalesce with cholangiocyte-lined bile ducts around lobule perimeter

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11
Q

What does the branch of portal vein bring?

A

Mixed venous blood from GIT (nutrients, bacteria & toxins) and spleen (waste products)

Hepatocytes process nutrients, detoxify blood & excrete waste

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12
Q

What does the bile duct do which is brought to lobules by portal triad?

A

Bile produced by hepatocytes drains into bile canaliculi

Coalesce with cholangiocyte-lined bile ducts around lobule perimeter

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13
Q

What is the functional unit of the liver?

A

Hepatic Acinus :

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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14
Q

What three regions can the acinus be split into?

A

Zone 1
Zone 2
Zone 3

  • Hepatocytes near outer hepatic lobule - Zone 1 : Receives most oxygen but most toxin risk. So it is where liver damage takes place first
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15
Q

What are the characteristics of Sinusoidal endothelial cells?

A
  • No basement membrane
  • Fenestrated
  • Allow lipids & large molecule movement to and from hepatocytes
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16
Q

What are the characteristics of Kuppfer cells?

A

‘Sinusoidal macrophage cells’

  • Attached to endothelial cells
  • Phagocystosis
  • Eliminate & detoxify substances arriving in liver from portal circulation
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17
Q

What are the characteristics of Hepatocytes, what roles are they involved in?

A
  • 80% of liver mass
  • Cubical
  • Synthesis e.g. albumin, clotting factors & bile salts
  • Drug metabolism
  • Receive nutrients & building blocks from sinusoids
  • could test for the albumin molecules to check liver function
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18
Q

What is the cholangiocytes?

A

Cells which Secrete HCO3- & H2O into bile

  • gall bladder epithelial cells
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19
Q

What is the Cori cycle?

A

Metabolic pathway in which lactate produced by anaerobic respiration in muscles is taken into the liver, converted by lactate dehydrogenase into pyruvate.

Gluconeogenesis then takes place = glucose

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20
Q

How does the synthesis of non-essential amino acids take place?

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A

Different keto-acids can be converted into multiple amino acids depending on the transaminase enzyme (vital for production of non-essential amino acids)

a-keto glutarate → e.g. glutamate, proline, arginine

Pyruvate → e.g. alanine, valine, leucine

Oxaloacetate → e.g. aspartate, methionine, lysine

21
Q

Why is the glucose-alanine cycle carried out in the liver?

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A

Muscles could use amino acids to produce energy but

Pyruvate to glucose conversion takes energy
Removal of nitrogen as urea takes energy

Transferring the problem to the kidney is saving energy

22
Q

Describe the glucose-alanine cycle

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A

Muscle cell : Glutamate ? plus pyruvate –> Alanine

Liver cell : Alanine into liver. ?

23
Q

Describe triglyceride metabolism occurring in the liver?

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A

Fatty acids go into the liver, Beta oxidation turns it into acetyl CoA

Series of reaction then gives Acetoacetate = tissue energy source

24
Q

Describe lipoprotein synthesis occurring in the liver?

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A

Glucose in the liver can turn into either:

  • -> Glycerol
  • -> Pyruvate –> Acetyl CoA

Acetyl CoA can then turn into either fatty acids or cholesterol.

If the glycerol + cholesterol combine lipoproteins are created

25
What is stored in the liver?
Storage fat soluble vitamins (A,D,E,K). Stores sufficient 6-12 month (except Vit K where store is small) Vit K essential blood clotting Storage of iron as ferritin. Available for erythropoeisis
26
Describe the two phases of detoxification occuring in the liver?
P450 enzymes Phase 1 (modification) – more hydrophilic Phase 2 (conjugation) – attach water soluble side chain to make less reactive
27
What two organs does the bile connect to?
Pancreas Liver
28
What are the uses of Bile?
Cholesterol homeostasis Absorption of lipids and lipid soluble vitamins e.g. ADEK Excretion of: xenobiotics/drugs cholesterol metabolites adrenocortical & other steroid hormones Alkaline phosphatase
29
Describe the composition of bile
``` Water - 97% Bile salts - 0.7% Inorganic salts - 0.7& Bile pigments - 0.2% Fatty acids - 0.15% Trace metals : Fe, Zn, Mn, Pb, Cu ```
30
Describe secondary secretion of bile by cholangiocytes?
Secrete 40% of total bile 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
31
What do Biliary transporters do?
Biliary excretion of bile salts and toxins on the apical and basolateral membranes of hepatocytes and cholangiocytes + Main transporters include: 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 MDR3 → phospatidylcholine.
32
Which two primary bile acids are synthesised in the liver?
Cholic acid Chenodeoxycholic acid
33
Which two secondary bile acids are produced when gut bacteria convert cholic acid and chenodeoxycholic acid?
Deoxycholic acid Lithocolic acid
34
What does it mean by Bile salts are 'Amphipathic' ?
Steroid nucleus planar- has 2x faces
35
How does emulsification lead to micelles by bile salts?
Fat globule is emulsified - broken down into bile salts and phospholipids Emulsification drops are created with these breakdown products Lipase and Colipase enzymes create these droplets into fatty acids and or monoglycerides These then form micelles: Bile salts surrounding the inner micelle made of phospholipids, fatty acids, monoglycerides
36
describe the structure of bile salts?
Form Micelles 1x surface hydrophilic domains (hydroxyl & carboxyl) - faces OUT → dissolves in water 2nd surface hydrophobic domains (nucleus & methyl) faces IN → dissolves in fat FFAs & cholesterol INSIDE 1x surface hydrophilic domains (hydroxyl & carboxyl) - faces OUT → dissolves in water 2nd surface hydrophobic domains (nucleus & methyl) faces IN → dissolves in fat FFAs & cholesterol INSIDE
37
How does emulsification lead to micelles by bile salts?
Emulsified droplets can be turned into fatty acids by Lapse and Colipase. The indivitual fatty acid - Monoglyceride can be trapped between bile salts = micelle Micelles are absorbed by the gut
38
Describe Enterohepatic circulation
95% bile salts reabsorbed from terminal ileum By Na+/bile salt co-transport Na+-K+ ATPase system 5% converted to secondary bile acids in colon: Deoxycholic acid absorbed 99% Lithocolic acid excreted in stool absorbed B.salts back to liver & re-excreted in bile
39
What causes the the release of cholecystokinin (CCK) What does it do?
Gastric contents (FFAs, AAs > CHOs) enter duodenum causing release of cholecystokinin (CCK) CCK causes gall bladder to contract
40
Describe the functions of the gall bladder?
Stores 50ml of Bile, concentrated and acidifies it Gallbladder contracts by CCK Binds to CCKA receptors & neuronal plexus of GB wall (innervated by preganglionic parasympathetic fibres of vagus nerve)
41
Describe the functions of the gall bladder?
Stores 50ml of Bile, concentrated and acidifies it Gallbladder contracts by CCK Binds to CCKA receptors & neuronal plexus of GB wall (innervated by preganglionic parasympathetic fibres of vagus nerve)
42
What two forms can bilirubin exist as? * biliverdin = green bile
Free BR - water insoluble, yellow pigment 75% BR from Hb (erythrocytes) breakdown 22% from catabolism of other haemoproteins 3% from ineffective BM erythropoies
43
What is conjugated/direct bilirubin?
Bilirubin diglucuronide
44
How is 85% of bilirubin excreted in stool?
Bilirubin --> Urobilinogen --> stercobilinogen --> stercobilin ( brown compound )
45
How is 15% of Bilirubin excreted trough the enterohepatic circulation?
BR--> deconjugaed --> lipohilic form : urobilinogen, stercobilinogen
46
How is 1% of Bilirubin excreted?
enters systemic circulation & excreted by kidneys
47
What is ERCP?
Endoscopic Retrograde Cholangiopancreatography
48
What is PTC?
Percutaneous Transhepatic Cholangiography (PTC): remove blockages

Gastroenterology (10 decks)

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