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COT pt. 2 > Lecture/Lab: Hematopoiesis & Bone Marrow > Flashcards

Lecture/Lab: Hematopoiesis & Bone Marrow Flashcards

1
Q

Sites of Hematopoiesis

A

Yolk Sac, Liver, Bone Marrow, Red Marrow

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2
Q

Yolk Sac Hematopoiesis

A

extraembryonic site
hematopoietic islands form here in the 3rd-4th week of gestation, peaking in 2nd month

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3
Q

Liver (and Spleen) Hematopoiesis

A

hematopoiesis begins here in the 5th week, peaks at 5-6 months gestation

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4
Q

Bone Marrow Hematopoiesis

A

hematopoiesis begins here in the
5th month of gestation, continues to adulthood

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5
Q

Red Marrow Hematopoiesis

A

limited to specific locations after
puberty
Location of RM: heads of long bones, rib cage, vertebral columns, pelvis, sternum

After puberty, red marrow typically is confined to the metaphyseal regions of long bones and to the axial skeleton. The crest of the iliac bone (the prominence one feels at one’s hips) is the preferred site for marrow biopsy as it is the part of the axial skeleton furthest away from CNS

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6
Q

Yellow Marrow vs. Red Marrow

A

Yellow- Higher proportion of adipose tissue
Red- Higher proportion of Hematopoietic cells

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7
Q

Macrophage Sequestration (Storage)

A
  • stored in spleen (as monocytes)
  • rapid deployment during tissue repair (ie myocardial infarction)
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8
Q

Neutrophil Sequestration (Storage)

A
  • “Marginated pool” PMNs (neutrophils) are adherent to endothelial cells
  • Postcapillary venules of lung is largest site of marginated (adhered) pool
  • normally 1/2 of PMNs are marginated (explains why CBC doesn’t tell the whole story)
  • released in response to stress,
    epinephrine
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9
Q

Lymphocyte Sequestration (Storage)

A

stored in secondary lymphatic organs (MALT, BALT)

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10
Q

Vasculogenesis

A

-The creation of a vessel out of CT
-MET event (mesenchymal to epithelial transition)
-Embryonic event, doesn’t happen in adults

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11
Q

Extraembryonic Hematopoiesis

A

Early blood and vessels come from the same source in extraembryonic (lateral sphlancnic) mesoderm

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12
Q

Blood island

A

collection of 1st progenitor cells of blood

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13
Q

Angiogenesis

A

-The sprouting of vessels from existing vessels
-Happens in adults
-Occurs in response to lack of oxygen

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14
Q

Tip cells

A

special endothelial cells that direct the formation of new vessels (via angiogenesis) by pulling stalk cells into vascular lumens

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15
Q

Hematopoietic tissue composition

A

The composition of hematopoietic tissue changes based on site, particularly for monocytes, neutrophils and dendritic cells, which are first found in bone marrow

This is expected because the needs of the embryo, fetus, and adult are different

Progenitors of the “organ-colonizing” cells are specific to liver

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16
Q

Composition of the vascular compartment of bone marrow

A

vascular sinus
(large, sinusoidal capillaries)

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17
Q

Composition of the hematopoietic compartment of bone marrow

A

stroma (supporting tissue):
- adipose tissue
- fibroblasts
- connective tissue
- endothelium
parenchyma (“functional” tissue):
- developing blood cells (hematopoietic islands)

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18
Q

Origin of each type of stromal cell

A

Derived from MSC
- Osteoblasts (secrete collagen & fibronectin for new bone)
- Adipocytes (store fat)
- Fibroblasts (secrete ECM)
- Endothelial cells (vascular lining)

Derived from HSC
- Osteoclasts (secrete protons, etc., to break down bone)
- Macrophages (phagocytic)

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19
Q

Stem cell

A

From Video:
A cell that can both renew itself (divide and create a daughter cell that is also a stem cell) and is totipotent (has ability to generate all of the cell lines that are found within that system)
ex: a cell that can create all of the cells of blood

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20
Q

Progenitor cell

A

From Video:
A cell that can renew itself, but cannot produce the whole lineage (multipotent)
ex: a cell that can produce lymphocytes, but none of the other blood cells

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21
Q

Precursor cell

A

From Video:
Cannot renew itself. If it divides, differentiation will go along with it. The daughter cells must be more differentiated than the parent cell. Restricted to one particular lineage of adult cells.

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22
Q

What two classes of progenitor cells are produced from hematopoietic stem cells? (classical view)

A

Common Myeloid Progenitor (CMP)
- erythrocytes
- platelets
- macrophages
- granulocytes

Common Lymphoid Progenitor (CLP)
- lymphocytes

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23
Q

What cells are produced from each class of progenitor cells? (classical view)

A

CMP (common lymphoid progenitor) which gives rise to:
– CFU- Eo (eosinophils)
– CFU- B (basophils)
– CFU -GM –> CFU-G (neutrophils) & CFU-M (monocytes)
– CFU-Megakaryocyte
– BFU-E (burst-forming unit - erythrocyte) –>CFU-E (erythrocytes)

CLP (common lymphoid progenitor) which gives rise to:
– CFU- LyT
– CFU- LyB

24
Q

What are the precursor cells in blood and what cells result from them?

A

The first precursor cell in each lineage is a “blast”.
– Proerythroblasts ultimately form erythrocytes.
– Myeloblasts ultimately form granulocytes.

25
What are CD markers and why are they important?
Because stem cells and progenitor cells are not morphologically distinguishable, they are recognized (and defined) in laboratories by using combinations of CD markers, made from monoclonal antibodies for surface proteins. CD markers such as CD-4 and CD-8 are famously used to distinguish different subtypes of T-cells. (from lecture notes) presence (+) or absence (-) or even the level of expression (lo, hi) of a CD molecule can be used to define a developmental stage. CD expression can be dependent on lineage and/or on stage of differentiation. CD4+ (Helper T cell) CD8+ (Cytotoxic T cell) CD3+ part of developing T cells
26
What are the erythrocyte precursor cells?
Proerythroblast, Basophilic erythroblast, Polychromatic erythroblast, Orthochromatophilic erythroblast, and reticulocyte
27
What is the main way to distinguish between erythrocyte precursor cells?
precursor cells are chiefly distinguished by their cytoplasmic coloration Less important characteristics are the size of the cell (goes from large to small), the size of the nucleus (big to small), the chromatin (euchromatic to heterochromatic)
28
Basophilic erythroblast
Contains all ribosomes, which make the cytoplasm basophilic We need a lot of ribosomes to make proteins (hemoglobin) Fine chromatin clumps in nucleus, basophilic cytoplasm Large (usually slightly smaller) cell with basophilic cytoplasm but lacking nucleoli
29
Polychromatic erythroblast
Begins to produce hemoglobin which is eosinophilic mix of ribosomes & hemoglobin Coarsechromatin clumps in nucleus, grey-blue cytoplasm, last stage for mitosis average-sized cell with a cytoplasm intermediate in color between basophilic and eosinophilic extremes
30
Orthochromatophilic erythroblast
Means "identical color" Same color as erythrocyte all hemoglobin average-sized cell with a cytoplasm equivalent in color to that of the reticulocytes
31
Reticulocyte
No nucleus, but does have some remnant organelles (not visible) On marrow smear, assume all RBCs are reticulocytes small, spherical eosinophilic cell lacking a nucleus. Remnants of intracellular organelles can be visualized with special stains Nucleus gone, fine strands in cytoplasm, frequency in peripheral blood depends on hematopoietic activity Shape is intermediate between spheroid and biconcave RNA and intracellular organelles still retained Not easily visualized in WrightGiesma stains – methylene blue is typically used for reticulocyte counts Very important part of a clinical blood workup. They will count reticulocytes which should be around 2%
32
Erythropoiesis
Erythropoiesis is the process by which red blood cells (RBCs) are produced in the bone marrow Erythropoiesis is regulated by substances normally present in marrow stroma: – G-CSF (granulocyte colony stimulating factor), – SCF (stem cell factor) – IL3 – The cytokine Erythropoietin (EPO) (made in kidney corticointerstitial cells), which is itself regulated by: * Oxygen levels * Renin-Angiotensin system (sensing blood pressure) * Other hormones, for example insulin
33
Erythrocyte progenitor cells
CMP – generates all non-lymphoid lineages. BFU-E – progenitor cell - requires several cytokines for survival - high proliferative potential - 14 days to RBCs in culture - motile – can be present in peripheral blood CFU-E – progenitor cell - highly dependent on EPO - 7 days to RBCs in culture - non-motile, found in marrow only
34
Proerythroblast
Nucleoli present in nucleus, no granules in cytoplasm Large cell with nucleoli and cytoplasm that can range from neutral to basophilic. In common preparations, it is not distinguishable from the myeloblast
35
What does increased reticulocyte count mean?
internal bleed or chronic anemia because marrow is pumping lots of reticulocytes into blood
36
How to reticulocytes and granulocytes leave the marrow?
Reticulocytes leave the marrow by piercing through endothelial cells Mitochondria and polysomes still finishing the production of hemoglobin Biconcave erythrocyte shape is formed within the circulation Reticulocytes leave the marrow, and are normally present at < 1.5% in peripheral blood. Granulocytes leave the marrow as either band cells or mature forms. Band cells are normally present at about 3% in peripheral blood.
37
What are the 3 types of granules that neutrophils have?
primary (azurophilic): lysosomes secondary (specific, i.e. neutrophilic, eosinophilic, basophilic) tertiary: chemotactic
38
How to distinguish blast cells? (proerythroblast and myeloblast)
Large cell, large nucleus, prominent nucleolus (large white spaces)
39
What is the order of the neutrophil and eosinophil lineage?
Myeloblast --> Promyelocyte --> Early neutrophilic/eosinophilic myelocyte --> Late neutrophilic/eosinophilic myelocyte --> Neutrophilic/Eosinophilic metamyelocyte --> Band cell (only for neutrophils) --> Mature neutrophil/eosinophil
40
What type of granule is present in each stage in the granulocyte lineage?
Myeloblast: no granules present Promyelocyte: primary (azurophilic) granules Early neutrophilic/eosinophilic myelocyte: secondary (specific) granules
41
Early neutrophilic/eosinophilic myelocyte
round nucleus specific granules begin to accumulate intracellularly. few specific granules
42
Late neutrophilic/eosinophilic myelocyte
kidney shape nucleus many specific granules
43
Neutrophilic/Eosinophilic metamyelocyte
V-shape nucleus V-shaped nucleus, i.e. containing an acute angle indentation. Basophilic metamyelocytes are not normally distinguished in LM because the basophilic granules (unlike eosinophilic granules) obscure the outline of the nucleus.
44
Band cell
C-shaped nucleus, without chromatin bridges immature form of neutrophil normally present in peripheral blood in small quantities, but over 2% can indicate pathology C-shaped nucleus (usually no acute indentations), but be careful to consider the orientation of the cell on the slide. Normally present at about 2% in peripheral blood.
45
Monocyte development
Progenitors: CFU_GM, CFU-M Precursors: monoblast, promonocyte In blood: circulating monocyte In tissue: macrophages, dendritic cells, osteoclasts
46
Lymphocyte development
Progenitors: CFU-Ly, CFU-LyB, CFU-LyT Precursors: lymphoblast, prolymphocyte In blood: circulating lymphocytes In tissue: Ly-B (B lymphocyte), Ly-T (T T lymphocyte), NK-cells (natural killer cells), interstitial plasma cells
47
Megakaryocytes
- Reside exclusively in bone marrow, are HUGE cells (100 μm in diameter) - Release pre-platelets into sinusoid/sinus capillary, which mature into platelets in circulation - Polyploid cells (one nucleus but many copies of DNA) as a result of endomitotic division in megakaryoblasts - Megakaryocytes with higher chromosome content produce more platelets than megakaryocytes with low chromosome content. - Platelet demarcation channels form in cytoplasm - 8000 platelets produced per megakaryocyte - Platelets (pre-platelets) are pinched off within the lumen
48
Life cycle of a platelet
platelets are pinched off from megakaryocytes in bone marrow & released into circulation (megakaryocytes are capable of altering the rate of platelet production over an entire order of magnitude) activated in response to clotting factors typically activated outside the circulation, or by exposure to basal surface of endothelia normally last about 10 days * “stored” in circulation
49
Primary lymphoid organs
Bone Marrow and Thymus Responsible for generating and maturing lymphocytes
50
Anemia
disorders of RBCs Reduction in the oxygen carrying capacity of the blood Causes include: – Blood loss via trauma or genetic defects – Kidney disease (kidney and liver make erythropoietin) – Bone marrow cancer Too few RBCs - Too few produced - Too many lost or destroyed Too many RBCs (polycythemia) - Right number of RBCs, but: Too small Too large Wrong shape (ex: sickle-cell anemia)
51
Leukemia
disorders of WBCs
52
Basic classification of leukemia
First letter: – A for Acute = few mature circulating WBCs – C for Chronic = abnormal function in circulating WBCs Second letter (which progenitor): – M for Myelogenous = affecting myeloid cells – L for Lymphocytic = affecting lymphocyte cells Third letter: – L for Leukemia = abnormal proliferation of leukocytes, sometimes called ‘cancer of the blood'
53
Acute Leukemias
Very few mature leukocytes (WBC’s) in blood. Blood may contain cells normally found in marrow. Marrow is full of rapidly dividing immature cells that do not differentiate. Anemia and bleeding are common as normal cells in marrow are affected by crowding. Treatments include drugs, radiation, bone marrow transplants and autologous stem cell transplants.
54
promyelocyte
smaller cell with nucleoli and azurophilic granules appearing, often near the Golgi.
55
mature neutrophil, eosinophil, basophil
segmented nucleus. Granulocytes usually leave marrow in their mature form, though in case of demand, late precursors may also leave.
56
Platelet demarcation channels
cytoplasmic structures which precede the formation of the proplatelet strings, are recognizable EM features of megakaryocytes

COT pt. 2 (11 decks)

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