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GI Final Exam > Disorders affecting the GI system > Flashcards

Disorders affecting the GI system Flashcards

1
Q

What is Hirschprung disease?

A

megacolon

  • colon doesn’t move
  • congenital absence of intrinsic ganglion cells in the myenteric and submucosal plexuses of the GI tract
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2
Q

What was the main gene discussed in Hirschprung disease?

A

RET

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3
Q

What is RET?

A
  • protooncogene… helps regulate cell growth

- responsible for MEN

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4
Q

What are MEN syndromes?

A

multiple endocrine neoplasia
-GOF mutations: gene product gets a new function or pattern of gene expression
-

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5
Q

What is the case with Hirschprung disease and the RET gene?

A

its a loss of function mutation that results in reduced or abolished protein function

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6
Q

What does the RET gene normally do?

A

makes a protein involved in signaling within cells.

-without it, we cannot transmit signals within cells

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7
Q

What does not develop porperly if RET isn’t working?

A

the enteric nervous system

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8
Q

What is Iron controlled by?

A

the need for hemoglobin

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9
Q

What transports iron in the body?

A

transferrin

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10
Q

what is iron stored in?

A

ferritin molecules (liver and heart)

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11
Q

How do we excrete iron?

A

trick question, we can’t physiologically

-blood loss….

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12
Q

What happens when too much iron is absorbed (iron in excess of transferrin binding capacity) ?

A

gets deposited in the liver, heart, and some endocrine tissues
-tissue damage and fibrosis

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13
Q

What happens when too many erythrocytes are destroyed?

A

iron accumulates in the reticuloendothelial macs first

-then tissue parenchyma after macs

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14
Q

What is secondary hemochromatosis?

A

a buildup of iron due to anemia, chronic liver diseases,

-usually a result ofhep C or alcoholism. Frequent blood transfusions

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15
Q

What gene is pretty important for iron absortion regulation?

A

HFE

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16
Q

What gene is responsible for most common form of iron overload: hemochromatosis?

A

HFE

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17
Q

What gene is responsible for most cases of jevenile hemochromatosis?

A

HJV

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18
Q

What gene is less common but with similar clinical presentation to HFE mutations?

A

TFR2

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19
Q

Which gene is responsible for hepcidin, and iron-regulating hormone critical for absorption?

A

HAMP

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20
Q

are there more things that increase Iron absorption or decrease it?

A

increase it

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21
Q

What are the 3 things that decrease iron absorption?

A
  • regular blood transfusions
  • high iron diet
  • iron loading vitamins
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22
Q

How does HFE work?

A

it regulates circulating iron uptake by regulation the interaction of TFR1/2 with transferrin

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23
Q

What is hepcidin?

A

a key regulator of the entry of iron into the circulation

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24
Q

What is transferrrin?

A

and iron binding blood plasma glycoprotein that controls the level of free iron in biological fluids

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25
Q

What is TFR1?

A

protein required for iron import form transferrin into cells by endocytosis

26
Q

What is TFR2?

A

a protein involved in the uptake of transferrin-bound iron into cells by endocytosis, although its role is minor compared to TFR1

27
Q

What is Ferroportin?

A

a transmembrane protien that transports iron fromthe inside of a cell to the outside of the cell, inhibited by hepcidin, and results in the retention of iron

28
Q

In states of iron deficiency, how are the levels of hepcidin?

A

low… we want to take in iron

29
Q

What does hepcidin do to stop iron intake?

A

it blocks ferroportin on the enterocyes and macrophages in duodenum

30
Q

If we have high iron levels and there is inappropriate contiued transport of iron into the plasma, what protein is there a mutation in?

A

HRE, HJV, or TFR2…. all resulin in low hepcidin levels

31
Q

What two molecules compete for a binding site at the TFR1 receptor?

A

Transferin and HFE

32
Q

Which molecule binds transferrin better? HFE or transferrin?

A

Transferrin

33
Q

What is the significance of unboune HFE on the cell surface?

A

stimulates expression of hepcidin

34
Q

What is the result of too much Fe2+?

A

more TFR2 will be made than TFR1

35
Q

What is the significance of TFR2?

A

transferrins bind it more than TFR1 becuase more TFR2 is expressed

  • TFR2 binding stimulates hepcidin expression
  • also, more HFE is free
36
Q

How many molecules does transferrin bind?

A

2 of them

37
Q

What is the result of decrease unbound HFE?

A

decreased TFR2

  • resulting in decrease HAMP expression
  • leading to increased Fe transfer out of enterocytes
38
Q

What are some characteristics of hemochromatosis?

A

late onset

  • nonspecific symptoms
  • progresses to hepatosplenomegaly
  • increased incidence of infections with decreased hepcidin
39
Q

What is the iron fist a sign of?

A

hemochromatosis

-but not everyone has it

40
Q

What is the problem with intracellular iron?

A

it leads to increased fre radical production and perosidation of P-lipids of organelles

  • cells di e
  • liver enzymes increase
41
Q

What does Serum ferritin measure?

A

the amount of iron contained or stored int he body

42
Q

What is total iron binding capacity?

A

tells us how well our body can bind to iron

-Siron/this is important for transferrin iron saturation percentage

43
Q

What is the treatment for reducing iron?

A

blood removal

44
Q

What is the Hereditary Hemochromatosis?

A

C282Y

-cysteine to Tyrosine at residue 282

45
Q

In wilson disease and MEnkes syndrome, what element are we worried about?

A

copper

46
Q

Where is copper absorbed?

A

in the stomach and duodenum

-bound to albumin and transported to the liver

47
Q

What 2 genes are involved in copper homeostasis?

A

ATP7A - expressed in most cells

ATP7B - in liver, brain, kidney, and placenta

48
Q

What is the major copper-carrying protein in the blood?

A

ceruloplasmin

-ATP7B is needed with copper as a co factor in order to make it from apoceruloplasmin

49
Q

What is ceruloplasmin?

A

an iron oxidoreductase important in iron absorption

-each ceruloplasmin carries 6 copper atoms

50
Q

What does ceruloplasmin promote?

A

iron loading onton transferrin which only binds Fe2+

51
Q

What does reduced copper lead to?

A

reduced Fe2+ transport that leads to an increased attempt to increase Fe2+ absorption

52
Q

Where are DMT1 and CRT1 located?

A

on both sides of the enterocyte

  • they let copper in
  • when copper’s in, it binds to proteins with a high affinity for it
53
Q

What is Menke’s syndrome?

A

ATP7A mutation

  • it’s normal function is to move Cu2+ from intestinal mucosa into blood
  • so, now uptake is impairs and Copper deficiency occurs
  • reactions can’t happen without it
54
Q

What is the sign of Menke’s syndrome?

A

twisted short light hair

  • temperature instability
  • failure to thrive
  • steel wool cleaning pad hair
55
Q

What does the vasculature in Menkes syndrome look like

A

Markedly toruous intracranial and extracranial vessels, which are characteristics of Menkes disease

56
Q

What are the skin and the occipital bone like in Menke’s disease?

A

skin is lax

and there are occipital horns

57
Q

What is Wilson Disease?

A

ATP7B mutation

  • prevents copper release from hepatocytes
  • apoceruloplasmin is degraded and ceruloplasmin levels decrease
  • iron levels affected
  • now, the only way to get rid of copper is to shed it through enterocytes which is not going to cut it
58
Q

What are the 2 ways to excrete copper?

A

metallothionein (MT) on enterocytes which get shed

-Ceruloplasmin binds excess copper in the liver which gets excreted with bile

59
Q

What is the clinical presentation of the Wilson disease?

A

progressive lenticular degeneration

  • bilateral softening of the lenticular nucleus
  • liver cirrhosis
  • depression
60
Q

What is the giveaway sign of wilson’s disease?

A

Kayser-Fleischer rings

  • copper deposited in descemet’s membrane of the cornea
  • reflects a high degree of copper storage in the body
61
Q

What is the defect in Menkes syndrome?

A

the intestinal absorption of copper

  • we can’t get it in
  • *decreased liver copper
  • but increased intestinal/kidney copper
  • we need to GIVE THEM COPPER
62
Q

What is the defect in wilson disease?

A

the biliary excretion of copper

  • we can absorb copper but we can’t get it out of the damn liver!
  • we need to CHELATE THE COPPER

GI Final Exam (10 decks)

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