Hematopoiesis Flashcards

1
Q

what is hematopoiesis?

A

formation and development of blood cells

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2
Q

what are the three components of hematopoiesis?

A

erythropoiesis
leukopoiesis
thrombopoiesis

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3
Q

how are cell numbers maintained?

A

interaction of hematopoietic organs and humoral regulatory molecules

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4
Q

what organs are involved in hematopoiesis?

A

bone marrow
thymus
lymph nodes
spleen
mononuclear phagocyte system
liver

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5
Q

where is most hematopoietic activity by birth?

A

bone marrow

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6
Q

in the embryo, where does erythropoiesis occur?

A

yolk sac

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7
Q

what functions does bone marrow serve?

A

major site hematopoiesis in adults
storage/reserve of mature cells
iron storage pool
lipid storage (inactive marrow)

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8
Q

where is active bone marrow retained in older animals?

A

epiphyses and in flat bones
sternum, pelvis, ribs, vertebrae

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9
Q

what cells is the thymus important for production of?

A

differentiation of T lymphocytes
production of lymphocytes and cytokines

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10
Q

what functions is the spleen important for?

A

proliferation lymphocytes
reservoir erythrocytes and platelets
removal/pitting red blood cells
extramedullary hematopoiesis

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11
Q

what is a common site of extramedullary hematopoiesis?

A

spleen
can occur elsewhere: lymph nodes, liver

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12
Q

what is extramedullary hematopoiesis?

A

hematopoietic activity in non-bone marrow tissues

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13
Q

what cells are central in the mononuclear phagocyte system?

A

tissue macrophages

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14
Q

why is the liver important?

A

vitamin storage
production of coagulation factors
production of erythropoietin precursor
can act as site of extramedullary hematopoiesis

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15
Q

what are the sites of hematopoiesis in fish and amphibians?

A

kidney
liver
spleen

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16
Q

can disruption of the microenvironment disrupt hematopoiesis, even if the hematopoietic cells themselves are normal?

A

yes

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17
Q

what cells control the release of blood cells from the marrow into the circulation?

A

endothelial cells lining the sinuses

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18
Q

what functions does the circulation serve for hematopoiesis?

A

nutrition
exit route for cells to enter bloodstream

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19
Q

what are some cytokines that control hematopoiesis?

A

colony-stimulating factors
interleukins
other factors

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20
Q

what does interleukin-1 stimulate?

A

myelopoiesis

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21
Q

is interleukin-1 pro-inflammatory or anti-inflammatory?

A

pro-inflammatory especially with TNF

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22
Q

what does interleukin-1 inhibit?

A

erythropoiesis: contributes to anemia of inflammation

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23
Q

where are stem cells primarily located?

A

in bone marrow

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24
Q

what are all blood cells derived from?

A

primitive mesenchymal cells known as pluripotent hematopoietic stem cells

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25
what is differentiation?
commitment of progenitor cells to a particular cell line or lines
26
what is maturation?
development of a differentiated cell into a functional blood cell
27
what does myeloid refer to?
may refer to granulocyte +/- monocyte cell lines or all non-lymphocytic hematopoietic cell lines
28
what is the majority of cells seen in bone marrow examination?
precursor cells
29
what are precursor cells subdivided into?
mitotic (proliferative) post-mitotic (maturation and storage)
30
who has large amounts of active bone marrow?
young animals
31
can active bone marrow expand back into long bone shafts/extramedullary shafts with increased need for hematopoiesis?
yes
32
what is pitting and which organ does it?
removal of abnormal structures from red blood cells without cell destruction spleen
33
what do nonhematopoietic cells provide?
structural support nutrients growth factors
34
what provides the scaffolding for hematopoietic cells?
reticular cells and trabeculae
35
what are cytokines?
proteins that modulate the functions of other cell types
36
what can produce cytokines?
most are produced by macrophages or lymphocytes also: endothelial cells, epithelial cells, connective tissue cells
37
can pluripotent hematopoietic stem cells enter circulation?
yes
38
does maturation or differentiation correspond with morphologic changes in the cells?
maturation
39
what happens with the size of erythrocytes as they mature?
decrease in size as they mature
40
at what stage does the cytoplasm of erythrocytes become visible?
rubricyte stage
41
how do macrophages support red cell precursors?
provide nutrients phagocytize defective cells and extruded nuclei
42
what is the first identifiable erythroid cell?
rubriblast
43
a rubriblast eventually produces about ____________________
16 mature red blood cells
44
what hormones regulate erythropoiesis?
erythropoietin interleukin-3 and colony-stimulating factors other hormones
45
what is erythropoietin?
glycoprotein
46
what produces erythropoietin?
peritubular interstitial cells of the kidney lesser extent hepatocytes and ito cells in liver
47
what does erythropoietin inhibit?
apoptosis of erythroid progenitor cells
48
what are platelets produced from in mammals?
megakaryocytes
49
what are platelets produced from in species other than mammals?
thromboblasts
50
what is thrombocytosis?
increased platelets or thrombocytes
51
what is thrombocytopenia?
decreased platelets or thrombocytes
52
why are megakaryocytes distinctive in bone marrow?
large size polyploidy
53
how are platelets released from mature megakaryocytes?
fragmentation of cytoplasmic extensions
54
what produces thrombopoietin?
bone marrow liver kidney
55
what is the main growth factor involved in megakaryocytes and platelet production?
thrombopoietin
56
thrombopoietin binds to circulating _____________, and thus the amount of free TPO is regulated by the total ______________________
platelets platelet mass
57
what is the first recognizable cell in the granulocytic lineage?
myeloblast
58
how many nuclear segments does the segmented cell have?
2-4 nuclear segments
59
what are reticulocytes?
polychromatophilic erythrocytes stained with new methylene blue stain immature red blood cells
60
why might chronic renal failure lead to anemia?
decreased erythropoietin levels
61
what does erythropoietin stimulate?
proliferation of mitotic erythroid precursor cells release of immature red blood cells into circulation
62
why can erythropoietin stimulate platelet synthesis?
structurally similar to thrombopoietin
63
what hormone decreases the response to erythropoietin?
estrogen
64
where can megakaryocytes be found?
lung spleen bone marrow
65
where does hematopoiesis occur in the fetus?
liver spleen thymus lymph nodes
66
what does inactive bone marrow consist of?
adipocytes endothelial cells reticular cells
67
what happens in lymph nodes with hematopoiesis?
lymphocytes and plasma cells can do other cell lines, uncommon
68
why does extramedullary hematopoiesis occur?
response to anemia/cytopenias common in normal too
69
where does hematopoiesis occur in reptiles?
spleen bone marrow
70
why are nerves important in bone marrow?
regulate vascular tone
71
______________ are a type of cytokine, many of which influence hematopoiesis
interleukins
72
what does interleukin-1 stimulate?
myelopoiesis
73
what are colony-forming units?
stem cells and committed precursor cells
74
when does a red cytoplasm in erythrocyte maturation become visible?
rubricyte stage
75
what is a polychromatophilic erythrocyte?
nucleus has been extruded cytoplasm is still kind-of basophilic: ribosomes and RNA
76
what are reticulocytes?
polychromatophilic erythrocytes stained with new methylene blue
77
what does erythropoietin inhibit?
apoptosis of erythroid progenitor cells
78
what is granulocyte maturation characterized by?
production of cytoplasmic granules and increasing nuclear segmentation
79
what does inactive marrow consist of?
adipocytes endothelial cells reticular cells
80
can lymph nodes act as a site for hematopoiesis of cells other than lymphcytes and plasma cells?
rarely
81
is it common to see extramedullary hematopoiesis in spleens of normal patients?
yes
82
what was the mononuclear phagocyte system formerly known as?
reticuloendothelial system
83
what happens in the mononuclear phagocyte system?
removal and destruction of blood cells hemoglobin degradation iron storage secretion of factors influencing hematopoiesis
84
where is release of blood cells from marrow controlled?
endothelial cells lining sinuses
85
can pluripotent hematopoietic stem cells enter circulation?
yes
86
how much of the bone marrow cells are pluripotent hematopoietic stem cells?
<0.2%
87
what is the morphology of colony-forming units similar to?
small lymphocytes
88
red blood cell precursors cluster around a _________________ in erythroid islands
macrophage: nurse cell
89
how many mature red blood cells does a rubriblast eventually produce?
16
90
with high erythropoietin levels, platelets may decrease as stem cells differentiate into the _________________________________
erythroid, rather than megakaryocyte, pathway
91
how does thyroxine stimulate erythropoietin production?
indirectly by increasing tissue oxygen demand