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Haematology > Haemopoiesis > Flashcards

Haemopoiesis Flashcards

1
Q

What is haemopoiesis?

A

Formation of BLOOD cells

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2
Q

What is the name for mature red cells?

A

Erythrocytes

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3
Q

Do mature red cells (erythrocytes) have a nucleus?

A

NO

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4
Q

What is the function of erythrocytes?

A

O2/CO2 transport

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5
Q

Do platelets have a nucleus?

A

NO

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6
Q

What is the role of platelets?

A

They are involved in primary haemostasis

Formation of the platelet plug

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7
Q

Name the 3 groups of white cells.

A
  • Granulocytes
  • Monocytes - macrophages
  • Lymphocytes
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8
Q

Name the 3 granulocytes.

A
  • Neutrophils
  • Eosinophils
  • Basophils
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9
Q

What do neutrophils have a role in?

A

Phagocytosis and acute inflammation

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10
Q

What do eosinophils do?

A
  • Destroy parasites.

* Modulate hypersensitivity reactions.

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11
Q

What do basophils do?

A

Modulate hypersensitivity reactions

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12
Q

What is the main type of monocyte?

A

Macrophage

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13
Q

What do macrophages do?

A

Modulate immune reactions, involved in phagocytic clearance, regulatory functions

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14
Q

Name the 3 types of lymphocyte.

A
  • B cells
  • T cells
  • NK cells
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15
Q

What are the 3 types of lymphocyte? And what are they involved in?

A 
B cells – humoral immunity (antibodies). 
T cells – cell-mediated immunity, regulatory functions. 
Natural killer (NK) cells – anti-viral/tumour.
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16
Q

What is erythropoiesis?

A

Production of red cells

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17
Q

What is thrombopoiesis?

A

Production of platelets

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18
Q

What is myelopoiesis/granulopoiesis?

A

Production of bone marrow and all the cells that arise with it

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19
Q

What is lymphopoeisis?

A

Production of lymphocytes

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20
Q

In a steady state ….

A

Cell loss is balanced by cell production

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21
Q

What is the lifespan of red cells?

A

120 days

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22
Q

What is the lifespan of neutrophils?

A

7-8 hours

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23
Q

What is the life span of platelets?

A

7-10 days

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24
Q

How many red cells are lost and produced per minute?

A

~2.5million

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25
Q

How many neutrophils are lost and produced per minute?

A

~1-2million

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26
Q

How many platelets are lost and produced per minute?

A

~1million

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27
Q

What do mature cells come from?

A

Precursor cells

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28
Q

What cell is formed just before the reticulocyte? What is the difference between these?

A

The late normoblast – contains a nucleus which is lost to form the reticulocyte

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29
Q

The late normoblast has a nucleus but when it becomes a reticulocyte it loses the nucleus but keeps some RNA

A

T

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30
Q

‘Cytoplasmic fragments of megakaryocytes’ refers to what cell type?

A

Platelets

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31
Q

Describe a megakaryocytic.

A

Has a polypoid nucleus, nucleus can divide many times without the cytoplasm having to also divide

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32
Q

What does the term ‘blast’ mean?

A

A NUCLEATED precursor cell

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33
Q

What are megakaryocytes?

A

Platelet precursor cells

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34
Q

What are the characteristic features of megakaryocytes/

A

They are polypoid

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35
Q

What is a reticulocyte?

A

An immediate red cell precursors

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36
Q

What is the characteristic appearance of reticulocytes?

A

‘Polychromasia’

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37
Q

What are myelocytes?

A

Nucleated precursors, arising between neutrophils and blasts

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38
Q

Where do all precursor cels come from?

A

The haemopoietic progenitor cell.

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39
Q

Where do progenitors and ultimately all haemopoietic cells come from?

A

Haemopoietic stem cells

40
Q

What cells can self-renew?

A

HSC - stem cells

41
Q

What happens as a haematopoietic stem cell as it divides?

A

It divides asymmetrically, producing 2 cells – one which has the exact same properties as the parent cell (self-renewal).

42
Q

What happens to self-renewal as you go down the haemopoietic tree?

A

It is lost

43
Q

What happens in the proliferation stage?

A

There is an increase of cell numbers

44
Q

What happens with regard to differentiation in haemopoiesis?

A

Descendents commit to one or more lineages

45
Q

What happens when descendents reach maturation?

A

They acquire self-renewal: a property of stem cells, lost in descendents

46
Q

What happens in apoptosis?

A

Descendents undergo cell death

47
Q

Outline the main developmental events in haemopoiesis.

A
  • Proliferation: increase in numbers
  • Differentiation: descendents commit to one or more lineages
  • Maturation: descendents acquire functional properties and may stop proliferating
  • Apoptosis: descendents undergo cell death
48
Q

Stem cell/progenitor/precursor cell concepts and terminology NOT rigid

A

T

49
Q

Overlap between developmental events (e.g proliferation and maturation can occur simultaneously)

A

T

50
Q

What are more primitive progenitors (e.g stem cells) like during steady-state haemopoiesis?

A

They are quiescent/dormant

51
Q

What cells are dormant during steady-state haemopoiesis?

A

HSC

52
Q

What 3 things can the term ‘myeloid’ refer to?

A
  • Marrow – e.g. ‘myeloid’ or marrow malignancy.
  • Lineage – e.g. non-lymphoid.
  • Granulocytes and precursors – myeloid:erythroid.
53
Q

What are haemopoietic stem cells derived from?

A

Mesoderm

54
Q

As early as when are circulating committed progenitors detectable?

A

Week 5

55
Q

What is the first site of erythroid activity? When does this stop?

A

Yolk sac - stops at week 10

56
Q

In utero, what are the other sites of haemopoiesis (aside from the yolk sac)? When does haemopoiesis start in each of these sites by?

A
  • Liver – starts by week 6.
  • Spleen – starts by week 12; probably only a small contribution in humans.
  • Bone marrow – starts by week 16.
57
Q

In adults, where does haemopoiesis usually occur?

A

Only in the axial skeleton and proximal parts of the long bones (i.e. humerus and femur).

58
Q

Describe what bone marrow is.

A

A complex organ, surrounded by a shell of bone with a neurovascular supply

  • Outer cortical bone – dense.
  • Inner trabecular bone – spongy.
59
Q

Projections of trabecular bone into the bone marrow increases SA

A

T

60
Q

What are the 3 main compartments of bone marrow which can be seen under a microscope?

A
  • Cellular
  • CT matrix
  • Vascular elements
61
Q

Name the 2 main cellular components of bone marrow.

A
  • Haemopoietic cells.

* Non-haemopoietic cells e.g. adipocytes, fibroblasts, osteoclasts, osteoblasts.

62
Q

What does the blood supply to the bone marrow come from?

A
  1. Nutrient artery.
    +
  2. Periosteal network.
63
Q

Instead of arterioles forming capillaries as usual, what happens in bone marrow?

A

Arterioles drain into ‘sinuses’.

64
Q

What are sinuses?

A

Wide venous vessels which open into larger central sinuses

65
Q

What is the difference between sinuses and capillaries?

A

Sinuses are larger and have a discontinuous basement membrane (allows blood cells to get out of bone marrow and into blood).

66
Q

What surrounds sinuses?

A

Endothelial cells, with gaps between them to allow escape of blood cells

67
Q

What is the importance of the adventitia cell that lines sinuses?

A

It has muscle filaments in it, so can contract to regulate the size of the sinus/gaps

68
Q

How do fully formed blood cells enter the circulation?

A

By passing through fenestrations in endothelial cells.

69
Q

What is the release of RED CELLS into the circulation associated with?

A

Sinusoidal dilatation and increased blood flow.

70
Q

What do neutrophils do when they require release into the circulation?

A

They actively migrate towards the sinusoid.

71
Q

What do megakaryocytes do in relation to sinusoidal blood vessels?

A

They extend long branching processes called proplatelets into the sinusoidal blood vessels

72
Q

Red marrow is haemopoietically active

A

T

73
Q

Yellow marrow is haempoietically inactive and fatty

A

T

74
Q

What is the relationship between yellow marrow and age?

A

Yellow marrow increases with age

75
Q

What does the decreased red marrow with increasing age result in?

A

Reduced marrow cellularity in older individuals

76
Q

How can marrow cellularity be estimated?

A

100-age = cellularity (%)

77
Q

What is the myeloid:erythroid ratio?

A

The relationship of neutrophils and precursors to proportion of nucleated red cell precursors

78
Q

What does the myeloid:erythroid ratio range from?

A

1.5:1 to 3.3:1 - more myeloid cells because the lifespan of neutrophils is less than that of red cells.

79
Q

Name a situation in which the myeloid:erythroid ratio might change?

A

Reversal in haemolysis as a compensatory response.

80
Q

What are the 2 main categories of things which regulate haemopoiesis?

A
  1. Intrinsic properties of cells (e.g. stem cells vs progenitor cells vs mature cells).
  2. Signals from immediate surroundings and periphery (microenvironmental factors).
81
Q

What does erythroid maturation occur around?

A

‘Nurse’ macrophages, in the form of islands - these provide nutrients

82
Q

What is neutrophil and its precursor maturation regulated by?

A

G-CSF (granulocyte-colony stimulating factor)

83
Q

What regulates the growth and development of megakaryocytes from their precursors?

A

Thrombopoietin.

84
Q

What do haematopoietic stem cells occupy?

A

Occupy a ‘niche’ (anatomical site) – this provides signals for expansion, differentiation or dormancy

85
Q

Where is the niche of haematopoietic stem cells found?

A

Around vasculature (arteriole or sinusoid) – provides access to different signals (cytokines)

86
Q

When is a HSC’s niche altered?

A

In disease states or with therapy

87
Q

What Ix’s are done for haemopoiesis?

A
  • blood count.
  • cell indices.
  • morphology (blood film).
88
Q

What is a less common test which Ix haemopoiesis?

A
  • bone marrow examination
89
Q

What test is sufficient when assessing mature cells?

A

Blood count/morphological assessment

90
Q

What can be studied in mature cells, but is not generally required?

A

The expression of antigens indicating lineage or stage of development

91
Q

What is immunophenotyping?

A

The study of antigen expression using specific antibodies

92
Q

What is the challenge with assessing haemopoietic progenitor/stem cells?

A

They are morphologically indistinguishable cells

93
Q

What tests can be used in the assessment of these rare populations of cells?

A
  • Immunophenotyping

* Cytochemistry

94
Q

What does immunophenotyping identify?

A

Patterns of protein (antigen) expression unique to a cell lineage.

95
Q

What does immunophenotyping use to identify patterns of proteins?

A

Antibodies (in combination) specific to different antigens

Haematology (26 decks)

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