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CR2 > Erythropoiesis and anaemia > Flashcards

Erythropoiesis and anaemia Flashcards

1
Q

What transports iron into enterocytes?

A

Ferroportin

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2
Q

In what form is dietary iron absorbed?

A

Fe2+ or as part of a protein, e.g. heme

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3
Q

In what form is free iron?

A

Ferrous Fe2+

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4
Q

What enzyme on the enterocyte brush border reduces Fe3+ to Fe2+?

A

ferric reductase enzyme

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5
Q

How many atoms of iron can each transferrin molecule carry? What form is the iron in?

A

Carry 2 ferric (Fe3+) iron ions

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6
Q

What is transferrin?

A

Iron-binding blood plasma glycoprotein that regulates the level of free iron in plasma and other extracellular fluids

Takes iron from the enterocytes –> blood –> bone marrow

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7
Q

What occurs when transferrin binds to transferrin receptors?

A
  1. iron is taken into the cell by endocytosis
  2. Once in the cell, the transferrin releases its iron ions
  3. taken up by Hb or ferritin molecules –> stores iron
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8
Q

When is serum transferrin measured?

A

in cases of suspected iron deficiency and in iron overload disorders

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9
Q

What are the different stages of RBC formation in a foetus?

A
  1. Mesoblastic stage:
    - 3rd week: nucleated RBC forms in yolk sac and mesothelial layer of placenta
  2. Hepatic stage:
    - 6th week: erythropoiesis mainly in liver and spleen
  3. Myeloid stage:
    - 3rd month: bone marrow becomes primary source of RBCs
    - exclusively the source of RBCs in last month of gestation
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10
Q

How does the formation of RBC change after birth?

A

Up to 5 years: RBCs formed in bone marrow of all bones

5-20/25 years: RBCs formed in the bone marrow of long bones (tibia + femur)

25+ years: RBCs formed in the bone marrow of membranous bones (rib, sternum, vertebrae)

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11
Q

What cytokine controls erythropoiesis?

A

EPO (erythropoietin)

mainly increase the speed of maturation of proerythroblasts

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12
Q

Where is EPO produced?

A

Fibroblast interstitial cells in the kidney (PCT)

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13
Q

What stimulates EPO release?

A

EPO secreting cells are sensitive to hypoxia
Hypoxia stimulates EPO release
This increases RBC production

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14
Q

What hormone increases EPO production?

A

Testosterone

- this is why males have slightly higher Hb levels than women

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15
Q

What does ESR actually measure? Why is it measured?

A

erythrocytes have a negative surface charge meaning that they repel each other
this means that erythrocytes do not stick together
HOWEVER inflammatory reaction or bacteria in the blood will increase the amount of fibrinogen in the plasma
fibrinogen reduces the -ve charge on the erythrocytes meaning that they clump together
Red cells clump to form stacks = ROULEAUX
these stacks settle faster
a raised ESR is a non-specific marker for infection

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16
Q

How long is the lifespan of a RBC? How are RBCs removed from the blood?

A

Lifespan: ~120 days

removed from the blood by macrophages as the pass through the spleen

17
Q

How is bilirubin formed from RBCs?

A

RBC: broken down into haem protein and globin proteins

Haem – haem oxygenase –> biliverdin – biliverdin reductase –> bilirubin

18
Q

How is bilirubin released into the blood?

A

Bilirubin = not very soluble

Binds to albumin in the splenic macrophages and the complex is released into the blood as unconjugated bilirubin

19
Q

What happens when unconjugated bilirubin reaches the liver?

A

It is attached to glucuronic acid by the hepatocytes to make it more soluble
when bound to glucuronic acid = conjugated bilirubin

20
Q

What happens when bilirubin becomes conjugated?

A

Passes in the bile to the small intestine
bacteria convert it into urobilinogen
most urobilinogen passes out of the body via the faeces

21
Q

Define anaemia in a female adult.

A

Hb level <11.5 g/dL

22
Q

Define anaemia in a male adult.

A

Hb level <13.5 g/dL

23
Q

Define anaemia in a child 6 months - 6 years.

A

Hb <11g/dL

24
Q

Define anaemia in a child/adolescent 6-14 years.

A

Hb <12 g/dL

25
Q

What are the symptoms of anaemia?

A
  • tiredness
  • fainting
  • SOB
  • worsening angina/claudication
  • palpitations
26
Q

What are the signs of anaemia?

A
  • pallor
  • tachycardia
  • bounding pulse
  • systolic flow murmur
  • cardiac failure
  • retinal haemorrhage
27
Q

What are the potential causes of anaemia?

A
  1. Reduced production of RBCs
    - iron deficiency
    - B12/folate deficiency
    - marrow infiltrate (cancer)
    - chronic disease (rheumatoid, cancer)
    - infections (HIV, parvovirus)
  2. Increased destruction of RBCs
    - haemolytic anaemia –> immune destruction or membrane/enzyme/Hb disorder
  3. Increased loss of RBCs
    - bleeding
28
Q

What is microcytic, normocytic and macrocytic anaemia?

A

Micro: <76 fl
Normo: 76-96 fl
Macro: >96 fl

29
Q

Iron deficiency leads to what type of anaemia?

A

Microcytic hypochromic anaemia

30
Q

What are causes of microcytic hypochromic anaemia?

A

Hookworm (most common)
diet
reduced RBC synthesis
increased iron loss

31
Q

What are the risk factors for iron deficiency anaemia?

A
  • gastric/bowel surgery
  • rectal bleeding
  • menorrhagia
  • change in bowel habit
  • appetite/weight changes
  • pregnancy/breastfeeding
  • unsupplemented vegan diets
  • female
  • aspirin/NSAIDs
  • age (premature or elderly)
  • hookworm**
32
Q

How is iron deficiency anaemia confirmed?

A

FBC - Low RBC count
Blood film - microcytic, hypochromic
Serum ferritin - is it low?
Serum iron binding capacity - is it low?

33
Q

How is iron deficiency anaemia treated?

A 
Haem containing proteins
Iron tablets (ferrous sulphate)
34
Q

What might cause normocytic anaemia?

A
  1. Anaemia from acute blood loss
    - shock syndrome
    - treat with blood transfusion and EPO treatment
  2. Anaemia from chronic disease
    - chronic inflammation, infection , cancer
    - reduced RBC lifespan
    - depressed erythropoiesis
    - poor marrow response to EPO
  3. Anaemia from abnormal haemolysis

CR2 (36 decks)

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