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28 Cards in this Set

  • Front
  • Back

Where is bile produced and stored?

- produced: liver




- stored: gall bladder

What are the components of bile (5)?

- bicarbonate




- cholesterol




- phospholipids




- bile pigments




- bile salts

Where are bile pigments derived from?




Where does this occur (4)?

- haem group from haemaglobin




- macrophages in the spleen, bone marrow and liver

What is the lifespan of RBCs?




What is a RBC composed of?




What happens to the globin monomers when they are recycled?

- 120 days




- 4x globin monomers, 4 iron-containing haem groups and 4 porphrin rings




- broken down to amino acids and reused

Describe the degredation and recycling of RBCs, including billirubin metabolsim (essay answer)

- begins with catabolisation of RBCs after 120 days or when they become damaged




- RBCs are phagocytosed by macrophages in the spleen and bone marrow, and Kupfer cells (macrophages) in the liver




- degredation causes the release of haem and globin. Globin is degraded into amino acids, and then re-enteres the blood stream to be used in erythropoiesis.




- haem is degraded to biliverdin by haem oxygenase. Billiverdin reductase then converts it into unconjugated billirubin and iron. Iron is either stored as ferritin, or transported in the blood bound to transferrin - to be used in erythropoiesis.




- unconjugated billirubin is lipid-soluble and therfore cannot be transported in the blood. To overcome this, it is becomes bound to albumin. It is then transported in blood to the liver, where glucoronic acid is used to produce conjugated billirubin. This makes billirubin water soluble so it can be excreted from the liver as bile.




- conjugated billirubin travels through bile canaliculi and bile ducts (ATP-dependant, rate-limiting step. Can thereore be pathological).




- bile containing conjugated billirubin is secreted into the duodenum, travelling through to the large intestine. In the small and large intestine, bacteria convert the conjugated billirubin into lipid-soluble urobilinogen, during a reaction which removes the glucoronic acid through a hydrolysis reaction




- 10-15% of urobilinogen is bound to albumin, reabsorbed into the blood. and transported back to the liver. Around 5% will again go through the same cycle back to the liver (the entero-hepatic urobilinogen cycle). The remaining 5-10% will be tranported to the kidneys, where it is converted to urobilin and excreted - this is what gives urine its yellow colour.




- the remaining 85-90% of the urobilinogen is oxidised by bacteria, forming stercobilin - this is what gives faeces its brown colour

Define emulsification




What are bile salts produced from?




Name 2 bile salts?

- the breakdown of fat globules in the duondenum into small droplets




- cholesterol




- glycholic acid and taurocholic acid

What is the purpose of emulsification?




How does it work?

- to produce small droplets so that the surface area is increasead, allowing lipases to act




- hydrophobic portion disperses large triglyceride droplets; hydrophilic portions prevents droplets reforming

Name 5 components of a micelle

- bile salts, fatty acids, monoglycerides, phospholipds, cholesterol, fat soluble vitamins

Why can excess conjugated billirubin not be excreted in urine?

- it can be transported in the blood - and therefore reach the kidneys - but blood albumin is too large to be filtered

The formation of micelles allows the digestion and adsorption of ___________ and ___________

- lipids




- and lipid-soluble vitamins (e.g. vitamins A, D, E and K)

Describe the general process of how lipids are digested and absorbed

- fat globules are emulsified by bile salts in the small intestine, producing smaller droplets

- lipases digests the fats, forming fatty acids (monoglycerides) and glycerol

- the fatty acids and glycerol unite with bile salts and phospholipids,...

- fat globules are emulsified by bile salts in the small intestine, producing smaller droplets




- lipases digests the fats, forming fatty acids (monoglycerides) and glycerol




- the fatty acids and glycerol unite with bile salts and phospholipids, forming micelles




- on encountering enterocytes (cells of the epithelial intestinal lining), the micelles dissociate and the fatty acids and glycerol are able to diffuse through the epithelial cell layer




- in the enterocyte, the fatty acids and glycerols are resynthesised into triacylglycerol, and then packaged with cholesterol and fat-soluble vitamins into chylomicrons




- the chylomicrons then move through the basolateral membrane by exocytosis, and then enter the circulation through lacteals

What regulates the flow of bile and pancretic juice into the duodenum

- sphincter of Oddi

Describe the role of fatty acids and amino acids, cholecystokinin, secretin and the ________nerves on the regulation of bile secretion

- fatty acids and amino acids in the duodenum stimulate the release of cholecystokinin from endocrine cells, whereas acids stimulae the release of secretin from endocrine cells




- cholecystokinin: causes the gall bladder to contract and the sphincter of Oddi to relax




- secretin: stimulates the liver to release bicarbonate ions into bile, and stimulates bile secretion

Why do bile salts have to be recyled?




How much of them is recycled?




Generally, what happens

- because there is not enough of them in the body




- 95%




- bile salts move from the digestive tract to the capillaries, and then transported back to the liver - the enterohepatic circulation

What are the normal adult reference ranges for total bilirubin and conjugated bilirubin?

- total bilirubin: <21umol/L




- conjugated bilirubin: <7umol/L

What level of hyperbilirubinaemia would be suffient for jaundice to be visible in the sclera?




What level of hyperbilirubinaemia would be suffient for jaundice to be visible in the skin?

- >30umol/L




- >100umol/L

Define pre-hepatic jaundice, hepatic jaundice and post hepatic jaundice

- pre-hepatic: anything that causes an increased rate of haemolysis - releasing billirubin into the blood




- hepatic: any condition that causes cholestasis (reduction or stoppage of bile flow) as a result of liver damage




- post-hepatic: conditions that cause cholestasis due to obstruction of the hepatic, cystic or common bile ducts

Is neonatal jaundice pre-hepatic, hepatic or post-hepatic?




What is the difference between physiological jaundice of the newborn, and haemolytic disease of the newborn?

- pre-hepatic




- physiological jaundice of the newborn occurs because foetal Hb needs to be destroyed and repaced with adult Hb. Because of and underdeveloped liver which may lack glucoronyltransferase, and inhibitors of conjugation in breast milk, there can be an elevated level of unconjugated billirubin in the liver.




- haemolytic disease of the newborn occurs when there is Rh incompatability between the child and the mother, causing haemolysis and very high levels of unconjugated bilirubin.

What is the biggest complication associated with haemolytic disease of the newborn?

- kernicterus: bilirubin crosses the blood-brain barrier and is deposited in basal ganglia and brain stem nuclei - causing brain damage

How would you treat physiological jaundice of the newborn and haemolytic jaundice of the newborn - and why?

- phyiological jaundice of the newborn: phototherapy




- haemolytic disease of the newborn: phototherapy and blood transfusion




- blue light changes unconjugated bilirubin to a water-soluble form. Blood transfusion is due to anaemia.

Give three causes of hepatic jaundice

- cirrhosis, hepatotoxic drugs (e.g. paracetemol) and viral hepatitis

Give three causes of post-hepatic jaundice

- gallstones




- pancreatitis




- pancreatic tumours

Give an example of the symptoms you would expect from a gallbladder in the following regions: cyctic bile duct, common bile duct and duodenal papilla

- cystic bile duct: painfult contractions




- common bile duct (no secretion in to the gut): steaorrhea, grey faeces and post-hepatic jaundice




- duodenal papilla (no bile or pancreatic secretion into the gut): malnutrition and acute pancreatisis

What would you expect to happen to the levels of unconjugated and conjugated bilirubin with pre-hepatic jaundice?




What would you expect to happen to the levels of unconjugated and conjugated bilirubin with hepatic jaundice?




What would you expect to happen to the levels of unconjugated and conjugated bilirubin with popst-hepatic jaundice?

- both would increase but with higher levels of unconjugated bilirubin




- both would increase but with higher levels of conjugated bilirubin




- normal unconjugated bilirubin but with slightly higher conjugated bilirubin

Which type of bilirubin (conjugated or unconjugated) should you not find in the blood and why?

- conjugated bilirubin




- bilirubin should only be in the blood while carried by albumin (unconjugated). Conjugaed bilirubin in the blood implies that it has leaked back into the blood due to problems in the liver (either hepatic or post-hepatic jaundice)

Diagnosis: obstructive/post-hepatic jaundice (gall stones?)

Diagnosis: obstructive/post-hepatic jaundice (gall stones?)

Further tests revealed raised anti-mitochondrial antibodies – characteristic of primary biliary
cholangitis (Hepatic jaundice)
Confirmed by histology of a liver biopsy

Further tests revealed raised anti-mitochondrial antibodies – characteristic of primary biliarycholangitis (Hepatic jaundice)Confirmed by histology of a liver biopsy