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Haematology Y3 > Haemopoiesis > Flashcards

Haemopoiesis Flashcards

1
Q

What is haemopoiesis?

A

The production of blood cells and platelets which occurs in the bone marrow.

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2
Q

What is the primary role of erythrocytes (RBC’s)?

A

O2 and CO2 transport

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3
Q

What is the primary role of platelets?

A

Primary haemostasis

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4
Q

What are the 3 main groups of WBC’s?

A

Granulocytes

Monocytes —-> macrophages

Lymphocytes

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5
Q

What are the 3 types of granulocytes and what are their functions?

A

Neutrophils
- Phagocytosis/acute inflammation

Basophils
- Modulate hypersensitivity reactions

Eosinophils
- Modulate hypersensitivity reactions
- Destroy parasites

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6
Q

Functions of macrophages?

A

Modulate immune reactions

Phagocytic clearance

Regulatory functions

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7
Q

What are the types of lymphocytes and what are their functions?

A

B cells - humoral immunity (antibodies)

T cells - cell-mediated immunity
- regulatory functions

Natural killer (NK) cell -Anti viral/tumour

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8
Q

What happens to cells when the body is in a steady state?

A

Cell loss is balanced by cell production

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9
Q

What is lifespan of red cells (x10^12/l)?

A

~120 days

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10
Q

What is lifespan of white cells (x10^9/l)?

A

~7-8 hours

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11
Q

What is lifespan of platelets (x10^9/l)?

A

~7-10 days

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12
Q

What are erythroblasts?

A

A polychromatic nucleated cell of red bone marrow that synthesises haemoglobin and that is an intermediate in the initial stage of red blood cell formation.

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13
Q

What are myeloblasts?

A

A unipotent (stem cell capable of only forming 1 cell type) precursor of the granulocytes.

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14
Q

What is the cell precursor for platelets?

A

Megakaryocytes

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15
Q

What are reticulocytes?

A

A precursor of the red blood cells that occurs immediately before the mature red blood cell.

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16
Q

What are myelocytes?

A

A nucleated precursor that occurs after myeloblasts and before neutrophils.

17
Q

Ultimately all haemopoietic cells come from haemopoietic stem cells. True/false?

A

True

They all originate from the haemopoietic progenitor cell

18
Q

Self-renewal is a feature not present in stem cells. True/false?

A

False

Self-renewal is the process by which stem cells divide to make more stem cells, perpetuating the stem cell pool throughout life.

A property of stem cells, lost in descendants.

19
Q

What is the definition of proliferation?

A

An increase in cell number.

20
Q

What is differentiation?

A

Descendants of the stem cells, commit to one or more functions (lineages).

21
Q

What is maturation?

A

The stem cell descendants acquire functional properties and may stop proliferating.

22
Q

What is apoptosis?

A

Descendants undergo cell death.

23
Q

Embryonically, where do the haemopoietic stem cells originate?

A

Mesoderm

24
Q

What is the site of erythroid activity?

A

The yolk sac and stops by week 10.

25
Q

When does the liver start becoming a site of haemopoiesis?

A

Liver starts by week 6 of gestation

26
Q

When does the bone marrow become a site of haemopoiesis?

A

Starts by week 16 of gestation and takes over as the dominant site of haemopoiesis before birth.

27
Q

Where does haemopoiesis occur in adults?

A

Restricted to the marrow within the axial skeleton, pelvis and proximal long bones.

28
Q

Where can a bone marrow biopsy be carried out in an adult and in a child?

A

Posterior iliac crest/sternum for an adult.

Tibia can be used in young child

29
Q

How is marrow cellularity reduced in older age?

A

Red (haemopoietically active) versus yellow (fatty inactive) marrow: increase in yellow marrow with age – results in reduction in marrow cellularity in older individuals

30
Q

What is the myeloid: erythroid ratio?

A

Myeloid: erythroid ratio: relationship of neutrophils and precursors to the proportion of nucleated red cell precursors (ranges from 1.5:1 to 3.3:1)

This can change (eg reversal in haemolysis as a compensatory response)

31
Q

What is the bone marrow?

A

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

32
Q

Components of the bone marrow?

A

Cellular compartments:
- Haemopoietic cells
- Non-haemopoietic cells eg, adipocytes (fat cells), ‘fibroblasts’ osteoclasts, osteoblasts.

Connective tissue matrix

Vascular elements:
- Nutrient artery and periosteal network.
- Arterioles drain into the “sinuses” - wide venous vessels, open into larger central sinuses.
- In contrast to capillaries, “sinuses” are larger and have a discontinuous basement membrane.

33
Q

Steps for the release of mature cells from the marrow?

A

Formed blood cells can pass through fenestrations in endothelial cells to enter circulation

Release of red cells is associated with sinusoidal dilatation and increased blood flow

Neutrophils actively migrate towards the sinusoid

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

34
Q

What are routine investigations for haemopoiesis?

A

Blood count, cell indices (measure the size, shape, and quality of your red blood cells).

35
Q

What is a less common (specialist) investigation for haemopoiesis?

A

Bone marrow aspiration

36
Q

What are the investigations used for mature (lymphoid and non-lymphoid cells) in haemopoiesis?

A

For non-lymphoid cells, the blood count/morphological assessment is often sufficient

For lymphoid cells, the expression of antigens indicating lineage or stage of development required. This study of antigen expression using specific antibodies is called immunophenotyping

Cytochemistry (enzymatic reactions)–rarely used.

37
Q

What are lymphoid and non-lymphoid cells?

A

Lymphoid cells are crucial for the adaptive immune response, providing a specific and targeted defence against pathogens.

Non-lymphoid cells contribute to the immediate, nonspecific defence mechanisms of the innate immune system.

38
Q

What is immunophenotying?

A

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

Use antibodies (in combination) specific to different antigens.

39
Q

How are cell surface antigens identified?

A

Using immunophenotyping to look for proteins i.e. CD34.

CD34 (Sialomucin) is a member of a family of single-pass transmembrane sialomucin proteins that show expression on early haematopoietic and vascular-associated tissue.

Haematology Y3 (39 decks)

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