1 Overview of Hematopoiesis Flashcards

1
Q

When in the fetus (weeks or months) does hematopoiesis occur only in a yolk sac? liver and spleen? only bone marrow?

A
  • <6 weeks
  • 6 wks to 7 months
  • 7 months onward
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2
Q

In infancy, what bones have hematopoiesis?

A

All bones… then fatty replacement and hematopoiesis only in central skeleton

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3
Q

The production of blood cells outside of the marrow space?

A

extramedullary hematopoiesis-most common in fetal spleen and liver

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4
Q

What supplies oxygenated blood to marrow?

A

nutrient arteries and periosteal capillary network

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5
Q

How does blood leave marrow?

A

thin endothelial lined sinusoids

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6
Q

What borders sinusoids in marrow?

A

adventitial reticular cells

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7
Q

What regulates passage of hematopoietic cells into systemic circulation?

A

adventitial reticular cells

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8
Q

What direction does the sinusoids drain?

A

periphery to center of the marrow–emptying into central vein

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9
Q

What produces structural scaffolding for bone marrow extravascular compartment??

A

stromal cells- fat cells, macrophages, reticular cells, fibroblasts

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10
Q

t-f, T cells and macrophages cannot produce regulatory factors or cytokines in bone marrow?

A

false

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11
Q

Are most pluripotent, self renewal hematopoietic stem cells very active?

A

No-quiescent

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12
Q

Is differentiation reversible?

A

No

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13
Q

What do HSC express on surface and are identified by?

A

CD34

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14
Q

Is there a higher frequency than stems for the committed progenitor cells?

A

Yes–myeloid and lymphoid

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15
Q

What cells (or stage) are recognizable by microscopic examination of the marrow?

A

Late precursors and mature blood cells

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16
Q

Are hematopoietic growth factors soluble or membrane bound?

A

Both—most are cytokines

17
Q

What produces hematopoietic GFs?

A

stromal cells, endothelial cells, HEMATOPOIETIC STEM CELLS, fat cells, macrophages

18
Q

Glycoprotein c-kit ligand is important for?

A

proliferation, migration and adhesion of stem cells

19
Q

What type of ligand is FLT-3?

A

tyrosine kinase ligand

20
Q

IL-3 does what to myeloid progenitors?

A

stimulates proliferation….GM-CSF does this also

21
Q

What are the major pathways caused by dimerization of receptors in hematopoietic cells?

A

JAK/STAT
MAP
PI3

22
Q

What is the earliest committed erythroid precursor?

A

BFU-e (burst forming unit-erythroid)

23
Q

What stage comes after BFU-e stage?

A

CFU-e (colony forming unit-erythroid)

24
Q

What is the main important growth factor for erythroid cells? what is it produced by?

A

erythropoietin (EPO)

produced by peritubular kidney cells in response to hypoxia

25
when is erthropoietin effective and what does it induce?
red cell production from BFU-e stage through maturation---about 25% of marrow cells are maturing red cells from the CFU-e onward stages
26
What are the stages of hemoglobin accumulation?
``` pronormoblast basophilic normoblast polychromatophilic normoblast orthochromic normoblast polychromatophilic red cell erythrocyte ```
27
How long do red cells live in circulation?
120 days
28
What is the major growth factor for granulocytes?
GM-CSF and IL-3
29
What does CFU-GM differentiate into?
CFU-G and CFU-M (GFs are G-CSF and M-CSF) | further maturation is caused by these same GFs until neutrophil and monocyte
30
Myeloid maturation steps?
myeloblast>promyelocyte>myelocyte>metamyelocyte>band>segmented neutrophil
31
What are dendritic cells, osteoclasts and macrophages derived from?
monocyte precursors
32
What is thrombopoiesis?
production of platelets (megakaryopoiesis too)
33
What are the progenitors for megakaryopoiesis?
BFU-MEG and CFU-MEG | GFs= IL-3, IL-6, IL-11, SCF
34
What GF has specificity for CFU-MEG and maturing megakaryocytic and promotes proliferation and differentiation? where is it synthesized?
Thrombopoietin (TPO), LIVER
35
What regulates production of thrombopoietin?
platelet mass and decreased platelet counts upregulate
36
Are megakaryocytic found in large numbers in the bone marrow?
no
37
What is cell growth, DNA replication and nuclear division without cytoplasmic division? example?
endomitosis-(megakaryocytes) | muliploid cells with nuclear content 8-32N
38
What are cytoplasmic fragments of megakaryocytic?
platelets--live for 7-10 days