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Semester 2-MEH > Session 5-Haemopoiesis, Erythropoiesis And Iron > Flashcards

Session 5-Haemopoiesis, Erythropoiesis And Iron Flashcards

1
Q

Where are RBCs, platelets and most WBCs produced?

A

Bone marrow

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2
Q

What is bone marrow aspirate?

A

Liquid marrow with some solid particles

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3
Q

What is haematopoiesis controlled by?

A

Hormones

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4
Q

Which system is responsible for the control and removal of blood cells?

A

Reticuloendothelial system (RES)

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5
Q

Which cells are part of the reticuloendothelial system?

A 
Monocytes
Macrophages 
Kupffer cells
Tissue histiocytes 
Microglial cells in CNS
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6
Q

What are the main organs of the reticuloendothelial system?

A

Spleen

Liver

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7
Q

What do reticuloendothelial cells in the spleen do?

A

Dispose of blood cells

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8
Q

In a full blood count, what information do the following give about blood cells:

1) haemoglobin
2) red blood count
3) mean cell volume

A

1) how effective they are
2) how many there are
3) how large they are

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9
Q

What are the functions of RBCs?

A

1) carry Hb
2) maintain Hb in its reduced (ferrous) state
3) generate energy
4) maintain osmotic equilibrium
5) deliver oxygen to tissues

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10
Q

Why do RBCs have a high SA:volume ratio?

A

More efficient gas exchange and increases flexibility as it moves through capillaries

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11
Q

What can a change in the shape of a RBC result in?

A

Cells can become more fragile and can burst and not be functional -> anaemia

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12
Q

Describe the structure of haemoglobin

A

Tetramer of 2 pairs of globin chains each with own haem group

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13
Q

What are the two configurations that haemoglobin can exist as?

A

Oxyhaemoglobin

Deoxyhaemoglobin

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14
Q

Which chromosomes are the globin gene clustered on?

A

11 and 16

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15
Q

When does foetal Hb switch to adult Hb?

A

3-6 months of age

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16
Q

What is the function of Hb?

A

Carriage of O2 from lungs to tissues and CO2 between tissues and lungs

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17
Q

True or false: haem molecule combines reversibly with O2 and CO2

A

TRUE

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18
Q

What do globin chains allow?

A

1) protect haem molecule from oxidation
2) confer solubility
3) permits variation in oxygen affinity

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19
Q

What shape is an oxygen dissociation curve?

A

Sigmoid

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20
Q

Complete the sentences:

Reduced pO2 is detected in interstitial ____________ cells in kidney. This leads to increased production of ________________ hormone. This hormone stimulates maturation and release of ____ cells from marrow. Hb then rises, pO2 rises and _________________ production falls.

A

Peritubular
Erythropoietin
Red
Erythropoietin

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21
Q

What are the two main metabolic pathways in red cells?

A

1) glycolysis

2) pentose phosphate pathway

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22
Q

What are the two forms of iron?

A

Available (functional)

Stored

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23
Q

What are the functional forms of iron?

A

Haemoglobin
Myoglobin
Tissue iron
Transported iron

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24
Q

What are the types of stored iron?

A

Ferritin

Haemosiderin

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25
Q

True or false: iron requirement increases with age

A

FALSE - decreases with age

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26
Q

Which cells ‘eat’ old senescent RBCs?

A

Macrophages

27
Q

Where is 95% of stored iron found?

A

Liver tissue-hepatocytes as ferritin

28
Q

Where is haemosiderin found?

A

In Kupffer cells

29
Q

True or false: humans don’t have a developed pathway for excretion of iron

A

TRUE

30
Q

Where can haem iron be obtained from?

A

Meat

31
Q

Where can non-haem iron be obtained from?

A

Pulses, nuts, grains etc

32
Q

Why is haem iron a better source of iron than non-haem iron?

A

Iron in haem iron is present in ferrous form, which is used by us.
Non-haem iron is ferric form and this needs to be converted to ferrous form

33
Q

How does non-haem iron exist?

A

Fe3+ (ferric)

34
Q

On which surface does Fe2+ bind transferrin?

A

Apical surface of duodenum and upper jejunum

35
Q

How is iron exported out of an enterocyte?

A

Ferroportin

36
Q

What do foetal enterocytes have receptors for?

A

Lactoferrin

37
Q

Iron is taken into cells by the binding of iron-transferrin complex to what?

A

Transferrin receptor (TfR)

38
Q

Which cells contain the highest number of transferrin receptors?

A

Erythroid cells

39
Q

Which vitamin enhances iron absorption?

A

Vitamin C (ascorbic acid)

40
Q

What inhibits iron absorption?

A

Precipitation/chelation of iron eg tea, chapatis, antacids

41
Q

What are the control mechanisms of iron absorption? (4)

A

1) regulation of transporters
2) expression of receptors
3) hepcidin and cytokines
4) crosstalk between epithelial cells and other cells like macrophages

42
Q

What is hepcidin?

A

Negative regulator of iron absorption

43
Q

Where is hepcidin:

1) secreted?
2) excreted?

A

1) liver

2) kidneys

44
Q

When is hepcidin synthesis increased?

A

Iron overload

45
Q

When is hepcidin production decreased?

A

High erythropoietic activity

46
Q

What is hepcidin production regulated by? (3)

A

1) HFE
2) transferrin receptor
3) inflammatory cytokines

47
Q

How does hepcidin inhibit iron?

A

Degrades ferroportin (protein involved in moving iron out of cells) and this prevents:

1) iron absorption from gut
2) iron release from macrophages

48
Q

What are the reasons for iron deficiency? (2)

A

1) insufficient intake/poor absorption

2) increased use (pregnancy, bleeding)

49
Q

What are the symptoms of anaemia?

A

1) tiredness
2) reduced oxygen carrying capacity (pallor, reduced exercise tolerance)
3) cardiac symptoms-angina, palpitations, development of heart failure

50
Q

What are the signs of anaemia? (4)

A

1) pallor
2) tachycardia
3) increased respiratory rate
4) epithelial changes

51
Q

True or false: iron deficiency leads to hypochromic and microcytic cells

A

TRUE

52
Q

What is the most commonly used measure of iron status?

A

Ferritin (acute phase protein)

53
Q

When is CHR used to test for iron deficiency?

A

If a patient has an infection

54
Q

What are the possible treatments of iron deficiency? (5)

A

1) dietary advice
2) oral iron supplements (with orange juice)
3) intramuscular iron injections
4) intravenous iron
5) transfusion (not unless there is severe anaemia)

55
Q

What can reduced iron produce?

A

Highly reactive hydroxyl and lipid radicals

56
Q

What is excess iron deposited as in tissues?

A

Haemosiderin

57
Q

What is haemochromatosis?

A

Disorder of iron excess resulting in end organ damage due to iron deposition

58
Q

What does haemochromatosis cause?

A 
Liver cirrhosis
Diabetes mellitus 
Hypogonadism 
Cardiomyopathy 
Arthropathy 
Skin pigmentation
59
Q

True or false: hereditary haemochromatosis is autosomal dominant

A

FALSE - recessive

60
Q

What is hereditary haemochromatosis a mutation in?

A

HFE gene

61
Q

What does HFE protein usually do?

A

Competes with transferrin for binding to transferrin receptor

62
Q

What happens to HFE in hereditary haemochromatosis?

A

Mutated HFE cannot bind so transferrin has no competition, too much iron enters cells

63
Q

How is hereditary haemochromatosis treated?

A

With venesection

64
Q

What is used to treat transfusion associated haemosiderosis?

A

Iron chelating agents

Semester 2-MEH (21 decks)

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