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Gastrointestinal > Bilirubin Pathways & Bile Production > Flashcards

Bilirubin Pathways & Bile Production Flashcards

1
Q

What is erythropoiesis?

A

Red blood cell synthesis

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2
Q

Where is erythropoietin made?

A

In the kidney - amount made depends on how well oxygenated the blood is

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3
Q

What does erythropoietin do?

A

It goes to the bone marrow to stimulate red blood cell production

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4
Q

What does RBC synthesis require?

A

iron, globin, vitamin B12, erythropoietin

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5
Q

What is a reticulocyte?

A

An immature RBC

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6
Q

What is the lifespan of a RBC?

A

120 days

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7
Q

Where do red blood cells go to die?

A

The liver, spleen or red bone marrow where they are broken down by macrophages

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8
Q

How does the macrophage know that the RBC is old?

A

There is low levels of neuraminic acid and higher levels of phosphatidylserine on the RBC

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9
Q

What are RBCs broken down into?

A

heme and globin

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10
Q

What happens to the globin?

A

it is broken down into amino acids that are reused for protein synthesis

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11
Q

What happens to the heme?

A

It is split up into iron and biliverdin

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12
Q

What enzyme converts haem to biliverdin?

A

haem oxygenase

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13
Q

What is the structure of haem oxygenase?

A

a dimer with a globin like structure

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14
Q

What happens to the iron?

A

It is packed with transferrin and goes to the liver or bone marrow

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15
Q

What colour is biliverdin?

A

green

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16
Q

What happens to the biliverdin?

A

It is broken down into bilirubin

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17
Q

What enzyme converts biliverdin to bilirubin?

A

biliverdin reductase

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18
Q

What is the structure of bilirubin?

A

An open chain of four pyrolle rings

19
Q

What colour is bilirubin?

A

yellow

20
Q

What is haemolysis?

A

pathological early breakdown of RBCs causing anemia and jaundice

21
Q

What causes haemolysis?

A

external attack on cells by bacteria (streptococcus and enterococcus), parasitic haemolysis (malaria), congenital or genetic factors

22
Q

What is haptoglobin?

A

A plasma protein that binds haemoglobin released from RBCs that are haemolysed at a site other than the spleen

23
Q

What is haemopexin?

A

a protein which carries haem to the liver

24
Q

What is low haemopexin a sign of?

A

haemolytic anemia

25
Q

What are the consequences of haemolysis?

A

unconjugated hyperbilirubinemia due to conversion of Hb to bilirubin exceeding the liver’s capacity to conjugate and excrete bilirubin, also increased sterobilin in the stool and increased urobilinogen in the urine, also reticulocytosis due to increased production of RBCs, also possible gall stones

26
Q

What are the symptoms of haemolysis?

A

pallor, fatigue, dizziness, hypotension, fever, pain in back and abdomen, jaundice, splenomegaly

27
Q

What causes the bluish purple colour of bruises in the first 1-2 days?

A

deoxy and met haemoglobin

28
Q

What causes the greenish yellowish colour of bruises after 5-10 days?

A

biliverdin

29
Q

What causes the brownish colour of bruises after 0-14 days?

A

bilirubin

30
Q

How is bilirubin transported in blood?

A

bound to serum albumin

31
Q

What happens to bilirubin in the liver?

A

It is conjugated by bilirubin UDP glucoronyltransferase

32
Q

How is conjugated bilirubin pumped into the bile cannaliculi?

A

cMOAT

33
Q

What is Dubin-Johnson syndrome?

A

a defect in cMOAT

34
Q

What is the treatment for Dubin-Johnson syndrome?

A

no treatment (what is Dubin-Johnson syndrome?)

35
Q

What is Crigler Najjar syndrome?

A

a lack of UDPGT - can’t conjugate bilirubin

36
Q

What are the symptoms of Crigler Najjar syndrome?

A

persistent jaundice, kernicterus (bilirubin encephalopathy and brain damage)

37
Q

What is the treatment of Crigler Najjar syndrome?

A

Uv light - flips the ZZ isomer of bilirubin to the E,Z isomer and the E,E isomer which are non toxic

38
Q

What happens to bilirubin in the bile?

A

It is broken down by bacteria to urobilinogen and stercobilin

39
Q

What happens to urobilinogen?

A

Some goes into the faeces, some (9%) is taken back up into the liver and some (1%) is transported to the kidney and excreted in urine

40
Q

What makes urine yellow?

A

urobilin - oxidated urobilinogen

41
Q

What makes faeces brown?

A

stercobilin

42
Q

What causes dark urine in hepatitis?

A

the 9% of urobilinogen that is normally taken back to the liver isn’t because of the back up and so the entire 10% is transported to the kidney and excreted in the urine

43
Q

What causes pale faeces in hepatitis?

A

The liver is backed up so is releasing less conjugated bilirubin so there is less stercobilin so faeces is paler

Gastrointestinal (40 decks)

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