Haemopoiesis Flashcards

1
Q

How many red blood cells are there?

A

3-5 x 10^12/ litre

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2
Q

How often are red blood cells replaced?

A

every 120 days

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3
Q

How many white blood cells are there?

A

2-6 x 10^9/ litre

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4
Q

How often are white blood cells replaced?

A

every 3-5 days

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5
Q

How many platelets are there?

A

150- 400 x 10^9/ litre

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6
Q

How often are platelets replaced?

A

every 10 days

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7
Q

Where is haemopoiesis in the first few days of life?

A

in the yolk sac

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8
Q

Where is haemopoiesis from 6 weeks to 7 months of life?

A

in the liver and spleen

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9
Q

Where is haemopoiesis throughout life after 7 months?

A

in the bone marrow - although can return to liver and spleen if bone marrow is too crowded - as a child it is in all bone marrow but as an adult it is in the axial skeleton

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10
Q

Why is the posterior superior iliac spine a good site for a bone marrow biopsy?

A

because it is in the axial skeleton so haemopoiesis will always be taking place there

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11
Q

What percentage of bone marrow is fat even when active haemopoiesis is taking place?

A

50%

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12
Q

Can a pluripotent stem cell be identified in the bone marrow?

A

no

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13
Q

Can colony forming units be identified in the bone marrow?

A

no - can only recognise maturational steps beyond colony forming units

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14
Q

If the bone marrow is in constant contact with circulating blood what stops maturing blood cells from entering the circulation prematurely?

A

the developing blood cells have specific adhesion molecules which bind to the bone marrow stroma to keep them there

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15
Q

What is the bone marrow stroma made up of?

A

cells and extracellular matrix

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16
Q

What is the role of the bone marrow stroma?

A

to provide the specific microenvironment for cell maturation

17
Q

What are haemopoietic growth factors?

A

glycoprotein hormones which act on specific receptors expressed on the maturing cells to signal maturation - there is a lot of redundancy in the growth factors with multiple growth factors acting on every part of the pathway

18
Q

Which haemopoietic growth factor acts on the beginning of the pathway at the pluripotent stem cell?

A

SCF

19
Q

Which haemopoietic growth factor produces eosinophils?

A

IL-5

20
Q

Which haemopoietic growth factor produces neutrophils?

A

G-CSF

21
Q

Which haemopoietic growth factor produces monocytes?

A

M-CSF

22
Q

Which haemopoietic growth factor produces red blood cells?

A

EPO

23
Q

Which haemopoietic growth factor produces platelets?

A

IL-6

24
Q

Which haemopoietic growth factors act across all lineages?

A

IL-3 and GM-CSF

25
Q

What is the two fold action of GM-CSF?

A

the actions of GM-CSF depend on the cell that it hits and which receptor its expressing - in the event of sepsis there is an upregulation of GM-CSF which will both activate mature cells to phagocytose and turn on production

26
Q

What is the mechanism of action of haemopoietic growth factors?

A

the growth factor binds to an extracellular receptor which turns on an intracellular second messenger system to activate transcription factors for cell proliferation, differentiation or activation

27
Q

What are haematinics?

A

agents required for red blood cell production - iron, folate and B12

28
Q

What are the features of red blood cells?

A

membrane, haemoglobin and enzymes

29
Q

What are the causes of iron deficiency?

A

inadequate diet, blood loss

30
Q

What are the causes of B12 deficiency?

A

inadequate diet, poor absorption and rarely an abnormality in a metabolic pathway

31
Q

Which haematinics are required for all cell production - not just red blood cells?

A

B12 and folate

32
Q

What are the causes of a folate deficiency?

A

inadequate diet (particularly in alcoholics), or drugs such as methotrexate