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LSS : Alimentary system > jaundice and liver failure > Flashcards

jaundice and liver failure Flashcards

1
Q

why do we produce bile?

A
  • Cholesterol homeostasis. - Dietary lipid/vitamin absorption - Removal of xenobiotics/drugs/endogenous waste product.
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2
Q

what is bile composed of?

A
  • Bile is 97% water and exists in an alkaline solution. - 500ml produced
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3
Q

what cells secrete bile?

A

60% by hepatocytes 40% by Cholangiocytes in the biliary tree

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4
Q

what are the roles of the bilary tree?

A
  • Alter pH, fluidity and modifies bile. - Facilitates passage of H2O into the bile via osmosis - Reabsorbs glucose and some organic acids - Secretes HCO3 -and Cl into the bile through CFTR. - contribute IgA antibodies
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5
Q

how is bile transported?

A
  • Apical transporters secrete the bile salts and toxins which also govern flow rate of bile
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6
Q

what happens if the transporters stop?

A

cholestasis

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7
Q

what are examples of the transporters?

A

BSEP – Bile Salt Excretory Pump ( active transport of the bile acids into the bile ) - MRP1 MDR related proteins

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8
Q

how many bile acids do we have what are they separated into?

A
  • 4 bile salts 2 primary and 2 secondary - primary is converted into secondary Cholic Acid → Deoxycholic Acid Chenodeoxycholic Acid → Lithocholic Acid
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9
Q

whata re 2 main functions of the bile?

A
  • Reduce surface tension of fats. - Emulsify fats
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10
Q

how do bile salts work?

A
  • they form micelles - due to they hydrophilic and hydrophobic nature
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11
Q

issue with bile salts?

A
  • they can be toxic in high concentrations
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12
Q

** look at the anatomy of the gall bladder and biliary tree :

A

************

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13
Q

what happens at the ampulla of the bile duct?

A

the sphincter of Oddi controls bile secretion into the 2nd duodenum.

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14
Q

what duct does the cystic duct join?

A

pancreatic duct before entering the duodenal papilla

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15
Q

what happens when you eat? what hormone is secreted?

A

Cholecystokinin

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16
Q

what are the functions of Cholecystokinin ?

A
  • Relax the sphincter of Oddi. -Contract the smooth muscle around gall bladder.
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17
Q

what is entrohepatic circulation?

A
  • where the liver cells transfer various substances including drugs from to the plasma to the bile
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18
Q

how does entrohepatic circulation affect drugs?

A

Can re-activate/prolong drug action - can affect drug dosage

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19
Q

what happens when bile cells undergo entrohepatic circulation?

A
  • 95% of bile salts reabsorbed in the terminal ileum - 5% are converted to secondary bile acids in the colon by colon bacteria - 3g of bile salts at any one time, secreted 2x a meal.
20
Q

what happens if someone does not have a terminal ileum?

A

– less resorption = more fatty stool as less bile salt excreted - malabsorption of fat soluble vitamins can cause irritable bowel

21
Q

what are functions of the gall bladder?

A
  • storage - acidification - concentrates bile bu H2O diffusion
22
Q

what are the effects of a Cholecystectomy ? ( gall bladder removal )

A
  • Gall Bladder aids digestion but is NOT essential. - they might get bowel problems -so they have to avoid very fatty foods
23
Q

what is bilirubin?

A

H2O insoluble, yellow pigment.

24
Q

what is bilirubin produced from?

A
  • 75% - Hb breakdown – in the spleen - 22% - Catabolism of other haem proteins. - 3% - Ineffective bone marrow erythropoiesis.
25
Q

how is bilirubin metabolised and excreted?

A
  • BR is bound to albumin - most of it dissociates in the liver - free BR enters the hepatocyte and binds to cytoplasmic proteins - in the hepatocyte it joins to glucoronic acid - Glucuronyl transferase catalyses production of bilirubin diglucuronide
26
Q

**show a diagram of this process?

A

*******

27
Q

what is total bilirubin?

A

free BR + conjugated BR

28
Q

what are Urobilinogens?

A

H2O-soluble, colourless derivatives of BR formed by gut bacterial action

29
Q

what happens to the bilirubin in the colon?

A
  • 50% of urobilinogen is passed in the stool as Stercobilinogen. - Faeces are brown as Stercobilinogen is oxidised to stercobilin
30
Q

what forms urobilinogens?

A

some unconjugated BR enters enterohepatic circulation and some forms urobilinogens

31
Q

what happens to the other 50% of urobilinogen?

A

Half of urobilinogen (UBR) formed is reabsorbed -20% of the 50% reabsorbed into the general circulation is excreted in urine.

32
Q

what is Cholestasis ?

A

cessation of bile flow - Can result in jaundice but isn’t a pre-requisite

33
Q

what is jaundice?

A

excess BR in the blood - yellow tinge to the skin, whites of eyes and mucous membranes

34
Q

what are the causes of jaundice?

A

pre hepatic and hepatic

35
Q

explain pre hepatic ? what is this characterised by? what investigations are carried out?

A

Increased quantity of unconjugated BR, due to: - dying of blood cells (haemolysis) - massive transfusion - haematoma - Ineffective erythropoiesis. - Hb drop without overt bleeding - Blood film

36
Q

what is the hepatic cause of liver?

A
  • when the hepatocytes are not working - due to : - defective uptake - defective conjugation - Defective BR excretion.
37
Q

what might cause hepatic cause of liver?

A
  • liver failure paracetamol OD - Intrahepatic cholestasis from sepsis,
38
Q

explain post hepatic jaundice? common causes? what happens to stercobilin?

A
  • defective transport of BR - due to common bile duct stones -gall bladder cancer - Stool pale as there is less stercobilin the urine is dark as the BR is sent to the kidneys
39
Q

what is a hereditary cause of jaundice?

A

– GILBERT’S SYNDROME - (autosomal recessive) - 5% of population - raise of UNCONJUGATED bilirubin in the blood stream. - due to 70% - 80% reduction in enzyme activity (Glucuronyl transferase ) which causes the conjugation of BR

40
Q

define acute liver failure?

A
  • the rate of hepatocyte death > regeneration rate can be two types - apoptotic (NO inflammation) - necrotic INFLAMMATION
41
Q

how can we subdivide liver failure?

A
  • Fulminant/Acute Hepatic Failure rapid - Sub-fulminant less rapid
42
Q

what is the cause of liver failure in the far east?

A

viral hepatitis

43
Q

**what are the differences between normal liver function and liver failure?

A

********

44
Q

what are some of the causes of death due to liver failure?

A

Bacterial/fungal infection

. o Circulatory instability.

o Cerebral oedema.

o Renal and/or respiratory failure.

o Coagulopathy.

45
Q

what is the only way of treating liver failure?

A
  • Liver transplant the ONLY therapeutic intervention of PROVEN benefit.
46
Q
A

LSS : Alimentary system (13 decks)

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