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Hematology > Chapter 1: Haemopoiesis > Flashcards

Chapter 1: Haemopoiesis Flashcards

1
Q

What is the main site of haemopoiesis in the first few weeks of gestation?

A

The yolk sac

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2
Q

From where is definitive haemopoiesis derived?

A

Definitive Haemopoiesis is derived from stem cells from the AGM region (aorta-gonads-mesonephros) called haemangioblasts seed the liver, spleen, bone marrow.

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3
Q

What are the major sites of haemopoiesis from 6 weeks to 7 months in utero?

A

The liver and the spleen.

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4
Q

When to the liver and spleen stop making blood cells?

A

About two weeks after birth.

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5
Q

What is the major site of haemopoiesis throughout most of life?

A

The bone marrow

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6
Q

How much of the bone marrow is haemopoietic during infancy?

A

All of the bone marrow is haemopoietic.

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7
Q

Where does haemopoiesis occur in the adult?

A

Mostly in the central skeleton. The peripheral marrow and up to 50% of the central skeletal marrow is converted to fat.

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8
Q

What is term for reactivation of haemopoiesis in the liver and spleen?

A

extramedullary haemopoiesis.

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9
Q

With what cell does haemopoiesis start?

A

The hematopoietic stem cell.

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10
Q

How common are hematopoietic stem cells?

A

1 in 20 million nucleated cells in the blood.

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11
Q

What is the known phenotypic characteristics of hematopoietic stem cells?

A

CD34+, CD38-, and they look like small or medium sized lymphocytes.

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12
Q

What cells do the hematopoietic stem cells give rise to?

A

Mixed myeloid progenitor (colony forming unit) and the lymphoid stem cell.

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13
Q

What is the importance of stromal cells in the bone marrow?

A

They provide a suitable environment for the survival of stem cells.

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14
Q

What are the stromal cells?

A

Adipocytes, fibroblasts, endothelial cells, and macrophages

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15
Q

What do stromal cells do?

A

They provide adhesion, growth factors, and ECM necessary for stem cells.

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16
Q

Can stem cells exit the bone marrow?

A

Yes they are found in the peripheral blood in low numbers

17
Q

What is necessary for the mobilization of stem cells?

A

They must cross the endothelium in the marrow. This process is aided by G-CSF, and GM-CSF.

18
Q

How is stem cell homing to particular tissues achieved?

A

Stem cell homing is achieved by chemokine gradients. Stromal derived factor-1 (SDF-1) is critical to this process.

19
Q

Which transcription factor commits cells to the myeloid lineage?

A

PU.1 is a transcription factor that commits cells to the myeloid lineage.

20
Q

What is GATA-1?

A

GATA-1 is a transcription factor that is important in erythropoietic and megakaryocytic differentiation.

21
Q

What are the functions of haematopoietic growth factors?

A

Haematopoietic growth factors can stimulate (1) differentiation, (2) maturation (3) prevent apoptosis, (4)affect function of mature cells.

22
Q

What is the major source of haemopoietic growth factors?

A

Stromal cells are the major source of haemopoietic growth factors. However, 90% of erythropoietin is produced by the kidneys, and thrombopoietin is produced mostly in the liver.

23
Q

What are the growth factors that act on stromal cells?

A

IL-1 and TNF

24
Q

What are the growth factors that act on pluripotential stem cells?

A

SCF and Flt-L

25
Q

What growth factors act on multipotential progenitor cells?

A

(1) IL-3
(2) GM-CSF
(3) IL-6
(4) G-CSF
(5) Thrombopoietin

26
Q

What growth factors act on committed progenitor cells?

A

(1) G-CSF
(2) M-CSF
(3) IL-5 (eosinophil csf)
(4) Erythropoietin
(5) Thrombopoietin

27
Q

What mediators inhibit haematopoiesis?

A

TGF-beta, and INF-gamma

28
Q

What three pathways are responsible for haematopoietic growth factor signal transduction?

A

(1) JAK/STAT
(2) MAP kinase
(3) Phosphatidylinositol 3

29
Q

What does erythropoietin stimulate?

A

stem cell production of erythrocytes

30
Q

What does thrombopoietin stimulate?

A

Stem cell production of platelets

31
Q

What does M-CSF stimulate?

A

M-CSF stimulates the differentiation of CFU-GM stem cells into monocytes.

32
Q

What does G-CSF stimulate?

A

G-CSF stimulates the conversion of CFU-GM stem cells into Neutrophils.

33
Q

What does IL-5 stimulate in Haematopoiesis?

A

IL-5 stimulates the production of eosinophils by stem cells.

34
Q

What are the principle families of adhesion molecules?

A

(1) Immunoglobulin superfamily (bind to antigens or surface)
(2) Selectins (leukocyte and platelet adhesion to endothelium)
(3) Integrins (involved in adhesion to ECM)

Hematology (12 decks)

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