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MEH > microcytic anaemia > Flashcards

microcytic anaemia Flashcards

1
Q

what are microcytic anaemias classified by visually

A

erythrocytes smaller than normal
paler than normal ( hypochromic)

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2
Q

what are the two causes of microcytic anaemia

A
  • reduced haem synthesis
  • reduced globin chain synthesis
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3
Q

what are the four causes of reduced haem synthesis

A
  • iron deficiency
  • lead poisoning
  • anaemia of chronic disease
  • sideroblastic anaemia
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4
Q

what is sideroblastic anaemia

A

inherited defect in haem synthesis

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5
Q

what are the two causes of reduced globin chain synthesis

A
  • a thalassemia
  • b thalassemia
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6
Q

what does TAILS stand for

A

T- thalassemia
A- anaemia of chronic
I- iron deficiency
L- lead poisoning
S- sideroblastic anaemia

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7
Q

what is iron require for

A
  • oxygen carriers in Hb and myoglobin
  • co-factors in enzymes:
    cytochromes
    krebs
    cytochrome P450
    catalase
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7
Q

why is free iron dangerous

A

free iron is toxic to cells but body has no mechanism for excreting iron

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8
Q

what is ferrous iron

A

Fe2+

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9
Q

what is ferric iron

A

Fe3+

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10
Q

what is the difference between ferric and ferrous iron

A

Fe2+ is reduced form while Fe3+ is oxidised form

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11
Q

what does dietary iron consist of

A

haem iron Fe2+
non-haem (mix of 2+ and 3+)

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12
Q

how much iron do we need a day in our diet

A

10-15 mg/day

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13
Q

where is iron absorbed

A

duodenum
jejunum

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14
Q

what is chyme

A

food passing through intestine

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15
Q

what form of iron is only absorbed

A

only ferrous iron (Fe2+) can be absorbed so ferric iron must be reduced to ferrous iron to be absorbed

16
Q

what are the ways iron is absorbed from the diet into enterocytes

A
  • haem readily absorbed converted to Fe2+ by haem oxygenase
  • Fe2+ is transported through DMT1 (divalent metal transporter) into cells
  • Fe3+ converted to Fe2+ by reductase using vitamin C
17
Q

where is iron stored

A

ferritin protein

18
Q

what transport ferrous iron into blood

A

ferroportin

19
Q

what is hephaestin

A

converts Fe2+ to Fe3+ in blood to be transported around the body

20
Q

what is hepcidin and where is it made

A

inhibits ferrroportin so less iron absorbed into blood

liver

21
Q

what is transferrin

A

transports Fe3+ around the body

22
Q

what factors negatively influence iron absorption

A
  • tannins in tea
  • phytates (pulses, chapattis)
  • fibre
  • antacids (gavison)
23
Q

what factors positively influence iron absorption

A

vitamin C and citrate

24
Q

how do the negative factors reduce absorption of iron

A

bind to non - haem iron in the intestine

25
Q

how do positive factors increase iron absorption

A
  • prevent formation of insoluble iron compounds
  • vit C helps reduce ferric to ferrous iron
26
Q

in what form is iron transported around the body

A

Fe3+

27
Q

where is functional iron found in the body

A
  • haemoglobin
  • myoglobin
  • enzymes
  • transported iron
28
Q

what is the soluble form of stored iron

A

ferritin

29
Q

what is the insoluble store of iron

A

haemosiderin

30
Q

where is haemosiderein accumulated.

A

macrophages, liver, spleen and marrow

31
Q

what is haemosiderin

A

aggregates of clumped ferritin particles, denatured proteins and lipid

32
Q

how is iron uptaken by cells

A
  • transferrin with Fe3+ binds to transferrin receptor and enters cytosol by receptor mediated endocytosis
  • Fe3+ in endosome released by acidic microenvironment and reduced to Fe2+
  • Fe2+ transported to cytosol by DMT1
  • Fe2+ stored in ferritin, exported by ferroportin or taken up by mitochondria for use in cytochrome enzymes
33
Q

where is most of the total daily iron requirement from

A

more than 80% of iron requirement met from recycling damaged or old RBC

34
Q

how is iron recycled

A

old RBC engulfed by macrophages bby splenic cells and kupffer ells

macrophages catabolise haem released from RBC

iron exported to blood (transferrin) or returned to storage pool as ferritin in macrophage

35
Q

how is iron absorption regulated

A
  • depend on dietary factors, body iron stores and erythropoiesis
  • sensed by enterocytes
  • regulation or transporters, receptors, hepcidin and cytokines
36
Q

what regulates hepcidin synthesis

A
  • increased by iron overload
  • decreased by high erythropoietic activity
37
Q

how does hepcidin regulate iron absorption

A

induces internalisation and degradation of ferroportin

38
Q

how does anaemia of chronic disease cause anaemia

A
  • inflammatory condition releases cytokines
  • increases production of hepcidin
  • ## inhibits ferroportin

MEH (12 decks)

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