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L.2 Haematopoiesis Flashcards

1
Q

What is Haematopoiesis?

A

The regulated development of blood cells from precursor stem cells in the bone marrow to mature cells in the blood.

It is a dynamic process of cellular production and development.

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2
Q

How many blood cells are produced by the bone marrow each day?

A

5-10 x 10^11 blood cells.

The production matches the number of cells at the end of their life-cycle, maintaining a steady state.

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3
Q

What type of stem cell do all peripheral blood cells derive from?

A

A pluripotent stem cell.

Pluripotent stem cells can continuously divide and differentiate into various types of cells or tissues.

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4
Q

What is the lifespan of erythrocytes (red blood cells)?

A

~120 days.

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5
Q

What is the lifespan of megakaryocytes (thrombocytes/platelets)?

A

7-10 days.

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6
Q

What is the lifespan of neutrophils?

A

1 day.

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7
Q

What is the lifespan of lymphocytes?

A

Many months or years.

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8
Q

What is the lifespan of monocytes?

A

Many months or years.

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9
Q

Where does Haematopoiesis occur in a fetus from 0-2 months?

A

In the yolk sac.

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10
Q

Where does Haematopoiesis occur in a fetus from 2-7 months?

A

In the liver and spleen.

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11
Q

Where does Haematopoiesis occur in a fetus from 5-9 months?

A

In the bone marrow.

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12
Q

In infants, where does Haematopoiesis primarily occur?

A

In the bone marrow.

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13
Q

In adults, which sites are involved in Haematopoiesis?

A

Vertebrae, sternum, skull, pelvis, proximal ends of femur.

These sites are essential for the production of blood cells in adults.

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14
Q

What happens to haematopoiesis sites as a person ages?

A

Haematopoiesis sites gradually decrease with age from the infant to the adult.

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15
Q

At what age does haematopoiesis occur in the shaft of the long bones?

A

To the age of 4 years.

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16
Q

What replaces the haemopoietic spaces in the long bones after the age of 4?

A

Fat cells.

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17
Q

By what age is haematopoiesis found in the sternum, ribs, pelvis, vertebrae, and skull?

A

By 18-20 years.

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18
Q

What is the term for haematopoiesis occurring in the sternum, ribs, pelvis, vertebrae, and skull?

A

Intramedullary haematopoiesis.

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19
Q

What is extramedullary haematopoiesis?

A

Haematopoiesis occurring in the liver and spleen.

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20
Q

In which conditions may extramedullary haematopoiesis occur?

A

Certain haematological conditions, i.e., haemolytic anaemias.

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21
Q

What is bone marrow?

A

Soft spongy vascular tissue that lies within the hollow interior of long bones.

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22
Q

What percentage of total body weight does bone marrow form in a healthy adult?

A

Around 5% of total body weight (around 2.6 kg).

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23
Q

What are the three compartments of bone marrow?

A
  • The Red Marrow (Haemopoietic tissue)
  • Sinuses or vascular spaces
  • The Yellow marrow (non-Haemopoietic tissue)
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24
Q

What is the function of the red marrow?

A

It is responsible for producing RBCs, WBCs, and platelets.

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25
What do the sinuses in bone marrow do?
Regulate the release of cells into the peripheral blood.
26
What primarily composes the yellow marrow?
Mainly consists of fat cells.
27
What type of cells are found in the yellow marrow besides fat cells?
Stromal cells like fibroblasts and macrophages.
28
What is the role of fibroblasts in yellow marrow?
They produce collagen.
29
What do macrophages in yellow marrow produce and store?
Produce growth factors and store iron.
30
What is the role of the bone marrow stroma?
It provides a necessary microenvironment for cell survival and differentiation.
31
What are some examples of cytokines/growth factors produced in the bone marrow stroma?
* IL-7 * GM-CSF * G-CSF
32
What types of extracellular matrix components are found in the bone marrow stroma?
* Fibronectin * Collagen type I/IV * Proteoglycans
33
What types of cells are involved in cell-cell interaction in the bone marrow stroma?
* Osteoblasts * Fibroblasts * Endothelial cells
34
What are totipotent stem cells?
Stem cells that come from embryos that are <3 days old and can develop into a new individual cell ## Footnote Totipotent stem cells can give rise to all cell types, including embryonic and extra-embryonic tissues.
35
What are pluripotent stem cells?
Stem cells that appear in embryos that are 5-14 days old and can develop into any cell type ## Footnote Pluripotent stem cells can differentiate into all three germ layers: ectoderm, mesoderm, and endoderm.
36
What are multipotent stem cells?
Stem cells that appear in embryos that are 14 days old and beyond, developing into Haemopoietic Stem Cells ## Footnote Multipotent stem cells are limited to differentiating into a narrower range of cell types.
37
What is the origin of all blood cells?
All blood cells arise from a haematopoietic stem cell (HSC) ## Footnote HSCs are crucial for the formation of red blood cells, white blood cells, and platelets.
38
What initiates the regulation of haematopoiesis?
Stem cell division, where one cell self-renews and the other differentiates ## Footnote This process is essential for maintaining the balance of stem cells and differentiated cells.
39
Approximately how many haematopoietic stem cells (HSCs) are present in humans?
About 2 x 10^4 HSCs, which is >0.1% of cells present in the bone marrow ## Footnote This small percentage reflects the specialized function of HSCs in blood cell production.
40
What is the proliferative capacity of one haematopoietic stem cell?
One HSC can produce one million (10^6) mature blood cells after 20 rounds of cell divisions ## Footnote This demonstrates the remarkable ability of HSCs to generate large numbers of cells.
41
What cell marker is associated with haematopoietic stem cells?
CD34 ## Footnote CD34 is used to quantitate HSCs for stem cell transplantation.
42
How many blood cells are produced in the bone marrow every day?
5-10 x 10^11 blood cells ## Footnote This high production rate is essential for maintaining blood homeostasis.
43
What factors regulate the production of blood cells in the bone marrow?
Cytokines, growth factors, hormones, and environmental factors (e.g., oxygen levels) ## Footnote These factors play critical roles in the differentiation and proliferation of blood cells.
44
What do haematopoietic growth factors interact with?
Specific receptors on the surface of haematopoietic cells ## Footnote This interaction is crucial for the regulation of blood cell production.
45
Why is regulation critical in haematopoiesis?
It determines the concentration of various lineages in the marrow and in the blood ## Footnote Proper regulation ensures balanced blood cell production.
46
How long does differentiation and maturation take in the bone marrow?
A number of days
47
What regulates proliferation in haematopoiesis?
Cytokines/growth factors/Colony Stimulating Factors (CSF) ## Footnote These factors are essential for the growth and development of blood cells.
48
What is the clinical application of EPO?
Stimulation of erythropoiesis in renal disease
49
What role does IL-2 play in clinical applications?
Enhanced killing of malignant cells and enhancement of the immune system
50
What factors are used for priming bone marrow for donation?
IL-3, G-CSF
51
Which factors are used in the treatment of bone marrow failure?
IL-3, G-CSF
52
From what type of stem cell are recognizable blood cells derived?
Pluripotent stem cell in the marrow
53
What are the two lineage-specific progenitor cells derived from pluripotent stem cells?
* Common myeloid progenitor cell * Common lymphoid progenitor cell
54
What cells are included in the common myeloid progenitor cell lineage?
* Erythrocytes (RBCs) * Megakaryocytes (Platelets) * Monocytes * Granulocytes (neutrophils, eosinophils, basophils)
55
What cells are derived from the common lymphoid progenitor cell?
* B lymphocytes * T lymphocytes * NK cells
56
What is the maturation sequence of the erythrocyte?
Stem cell -> Proerythroblast -> Early erythroblast -> Late erythroblast -> Normoblast -> Reticulocyte -> Erythrocyte
57
What happens to the size of the erythrocyte during maturation?
The size of the cell decreases
58
How does the cytoplasm volume change during erythrocyte maturation?
The cytoplasm volume increases
59
What happens to the nucleus during erythrocyte maturation?
Initially present, it decreases in size and eventually vanishes
60
What do erythrocytes do with their nucleus and organelles during maturation?
They extrude their nucleus and organelles, making more room for haemoglobin
61
What is the lifespan of red blood cells?
120 days
62
What does the term 'blast' indicate in haematopoiesis?
A large proliferating cell
63
What is the maturation process of platelets?
Common myeloid progenitor -> megakaryoblast -> promegakaryocyte -> megakaryocyte -> thrombocytes
64
How long do platelets live?
7-10 days
65
What is the primary function of erythrocytes?
Transport of O2 and CO2 and to act as a buffer
66
What is the role of leucocytes?
Protect the body against infection
67
What is the function of neutrophils?
Fight bacterial infection
68
What do lymphocytes primarily fight?
Viral infections
69
What is the function of eosinophils?
Respond to allergic reactions
70
What is the role of thrombocytes?
Involved in haemostasis, which is the response to tissue injury
71
What can cause unbalanced haematopoiesis?
Damage or disease of the bone marrow caused by drugs, radiation, infiltrating cancer, or viruses
72
What condition can underproduction of blood cells lead to?
Aplastic Anaemia
73
What condition can overproduction of blood cells lead to?
Leukaemia
74
What test is commonly used to suggest blood disorders?
Full Blood Count
75
What do automated haematology analysers measure and count?
Cells
76
What can examination of the blood film reveal?
Morphological abnormalities undetectable by the analyser
77
How can significant blood abnormalities be further investigated?
Examination of the Bone Marrow – aspirate & trephine biopsy specimens
78
What are the three main sampling sites for bone marrow?
• Posterior iliac crest • Anterior iliac crest • Sternum ## Footnote These sites are commonly used for obtaining bone marrow samples.
79
What tests are typically requested for bone marrow evaluation?
• Bone Marrow Aspirate • Bone Marrow Trephine Biopsy ## Footnote These tests help in assessing the condition of the bone marrow.
80
What does the M:E ratio represent in bone marrow assessments?
The ratio of all granulocytic plus monocytic cells (Myeloid) to all erythroblasts (Erythroid) ## Footnote Normal Ratio is 1.3 - 4.6.
81
What additional information is specified in a bone marrow aspirate report?
The M:E ratio and the percentage of lymphocytes and plasma cells. ## Footnote This information is crucial for diagnosing various conditions.
82
What is the minimum number of cells that should be counted for a differential in bone marrow analysis?
At least 200-300 cells. ## Footnote This ensures a reliable differential count.
83
Why can cellularity not be assessed without knowing the patient's age?
Because cellularity varies significantly with age. ## Footnote For example, a young child has about 80% hematopoietic cells, while a 75-year-old has around 30%.
84
What characterizes hypercellular bone marrow?
Fat cells replaced by haematopoietic cells (leukaemia). ## Footnote This indicates an increased production of blood cells.
85
What is the normal cellularity composition of bone marrow?
50% fat cells and 50% haematopoietic cells. ## Footnote This balance is essential for normal function.
86
What indicates hypocellular bone marrow?
Haematopoietic cells replaced by fat cells (aplastic anaemia). ## Footnote This condition leads to reduced blood cell production.
87
How is normal bone marrow iron stained for evaluation?
With Perls Prussian Blue. ## Footnote This method helps visualize iron stores in the marrow.
88
What is the primary use of most absorbed iron in the bone marrow?
For erythropoiesis. ## Footnote This process is critical for the production of red blood cells.
89
What percentage of absorbed iron is stored in the mononuclear phagocyte system?
About 10 to 20%. ## Footnote This iron is also recycled into erythropoiesis.
90
Fill in the blank: Normal cellularity of bone marrow consists of _____ fat cells and _____ haematopoietic cells.
50% fat cells; 50% haematopoietic cells. ## Footnote This reflects a healthy bone marrow environment.

Haematology Lectures (17 decks)

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