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Microscopic Anatomy > Unit III- Hematopoiesis I > Flashcards

Unit III- Hematopoiesis I Flashcards

1
Q

Preparation of a blood smear

A
  • place a drop of blood on a microscope slide
  • take a second slide and place it in contact with first slide at an angle of 45 degrees
  • move second side over the first until it makes contact with the drop of blood
  • spread blood by moving oblique slide uniformly along fixed slide
  • air dry
  • fixed dried smear in methanol
  • stain with Romanovsky stain
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2
Q

Romanovsky Type Blood Stain

A
  • basic: methylene blue (RNA), stains cytoplasmic with cytoplasmic RNA heavenly blue
  • azure B (DNA and GAGs)- stains nuclei purple, stains cytoplasmic granules of basophils and lysosomes crimson

acidic:
eosin- (proteins), strains hemoglobin of rbc red pink

variations: Wright’s, Giemsa, May-Grunwald

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3
Q

Regions of typical blood smear

A
  • beginning or head: red blood cells overlap, leukocytes appear to have shrunk
  • end or tail-cells will appear over-stretched, distorted or broken
  • middle- red blood cells slightly separated, leukocytes will spread but intact, area of choice for study
  • observe in oil immersion 100x for detailed study of cell
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4
Q

General considerations of blood cells

A
  • life span is relatively short
  • they must be continuously produced
  • production of blood cells is known as hematopoiesis (granulopoiesis- development of granulocytes, erythropoiesis- development of eythrocytes)
  • hematopoietic organs- bone marrow, lymphoid organs, liver is a major hematopoietic organ in the fetus
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5
Q

Monophyletic/ Polyphyletic theory

A

Mono- all blood cells arise from a common pluripotential stem cell- most widely held theory today
-Poly- each type of blood cell arises from its own stem cell- not a widely help theory today

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6
Q

blasts

A
  • precursor cells
  • each blast gives rise to one type of blood cell (monopotential)
  • morphology:
  • relatively large cell with a diameter of 10-15 um
  • contains a large euchromatic nucleus (several nucleoli may be seen, large nucleo-cytoplasmic ratio)
  • numerous ribosomes in the cytoplasm- cytoplasm will appear pale blue in blood smear
  • no cytoplasmic granules
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7
Q

Neutrophil differentiation

A
  • condensation of nuclear chromatin (disappearance of nucleoli)
  • lobulation of nucleus
  • appearance of cytoplasmic granules (primary and secondary)
  • decrease in cytoplasmic basophilia
  • decrease in descriptive stages: blast (myeloblast), neutrophilic promyelocyte, neurophilic myelocyte, neutrophilic metamyelocyte, neutrophilic ban, mature neutrophil
  • normally blasts, promyelocytes, myelocytes and metamyelocytes are found only in bone marrow
  • bads and adult neutrophils appear in peripheral blood
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8
Q

Neutrophilic promyelocyte

A
  • relatively large cell- 10-15 um
  • spherical nucleus with slight chromatin condensation
  • nuclei are often observed
  • cytoplasmic granules- primary (azurophilic) granules, primary lysosomes- contain hydrolytic enzymes (acid phosphatase +), will be numerous at end of promyelocyte stage
  • capable of mitosis
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9
Q

Neutrophilic myelocyte

A
  • -round or oval nucleus
  • more heterochromatic
  • no longer makes azurophylic granules
  • appearance of specific granules- secondary granules appear and increase in number, contain lysozyme and lactoferrin, cause cytoplasmic color change from heavenly blue to salmon
  • capable of mitosis
  • ability to replicate DNA and to synthesize RNA gradually decreases- chromatin becomes more condensed, cytoplasmic basophilia decreases
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10
Q

Neutrophilic metamyelocyte

A

-no longer able to synthesize nucleic acids (DNA and RNA)
-no longer able to undergo mitosis
-morphology:
indented nucleus
chromatin is more condensed
no evidence of cytoplasmic basophilia
cytoplasmic granules- numerous small secondary granules, few large primary granules

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11
Q

Neutrophilic band

A
  • morphology
  • further bending of nucleus (indentation exceeds 1/2 the diameter of round nucleus)
  • chromatin is quite condensed
  • cytoplasm resembles that of mature neutrophil
  • can be found in normal peripheral blood
  • 1-5% of total leukocytes
  • percentage of bands in peripheral blood is a rough indicator of the rate of neutrophil production- “shift to the left”
  • incapable of mitosis
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12
Q

Mature neutrophil

A

-when the segments between lobes have become thin heterochrmoatic filaments, the band has differentiated into a mature neutrophil

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13
Q

Kinetics of neutrophil production

A
  • process takes 9-14 days (blast to adult)
  • cells spend less than 1 day in circulation- exchange between circulating and marginating pools
  • cells leave blood vessels and enter surrounding tissues (diapedesis)- paracellular and transcellular
  • live in the surround tissue about 5 days
  • total life span - 15-20 days
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14
Q

Eosinophil and basophil productuin

A
  • during myelocyte stage specific granules appear in developing eosinophils and basophils
  • these granules are larger than specific granules of neutrophils
  • eosinophilcs- specific granules are almost black when they first appear, become pink-red as maturation continues
  • basophils- specific granules stain purple in smears
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15
Q

Red bone marrow

A
  • site of hematopoiesis
  • location: flat bones of body- sternum, vertebrae, ribs, clavicles, bones of pelvis, bones of skill
  • composition: blood vessels, discontinuous sinusoids, cords of hematopoietic cells- site of blood cell maturation
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16
Q

Hematopoietic stem cell niche

A
  • interactive structural unit- localized supporting cells, ECM (fibronectin, laminin, agrin), soluble factors derived from supporting cells
  • nurtures stem cells and maintains their properties
  • facilitates activity of stem cells
  • found in association with spongy bone- osteoclasts create spaces in bone surface, osteoblasts required for stem cell localization, endothelial cells, pericytes, bm macrophages may also be involved
  • alterations may lead to myeloproliferative disease- preleukemic condition
  • other stem cells
17
Q

Yellow bone marrow

A
  • not active in hematopoiesis
  • location: medullary cavities of all other bones in the adult
  • consists mostly of adipose cells
  • functions: storage of reserve energy, reserve of hematopoietic tissue
18
Q

Erythrocyte blast

A
  • each blast gives rise to one type of blood cell (monopotential)
  • morphology:
  • relatively large cell with a diameter of 10-15 um
  • large euchromatic nucleus- several nucleoli may be seen, large nucleo-cytoplasmic ration
  • numerous ribosomes in the cytoplasm- cytoplasm will appear pale blue in blood smear
  • no cytoplasmic granules
19
Q

Erythrocyte Differentiation

A
  • decrease in cell volume
  • decrease in nuclear diameter
  • increase in heterochromatin
  • disappearance of nucleoli
  • loss of nucleus
  • decrease in cytoplasmic basophilia
  • increase in cytoplasmic eosinophilia- amount of hemoglobin increases
20
Q

Descriptive stages

A

1) blast (erythroblast)
2) basophilic erythroblast
3) polychromatophilic erythroblast
4) normoblast
5) reticulocyte
6) orthochromatic erythroblast
7) mature erythrocyte (red blood cell)

21
Q

Basophilic erythroblast

A
  • cell is smaller than a blast
  • nucleus- smaller than blast, checkerboard appearance of chromatin, nucleoli will disappar
  • cytoplasm- intensely basophilic (navy blue), large increase in free ribosomes, preparing to produce globin portion of hemoglobin
  • lasts 1-2 days
  • capable of 1-2 mitotic divisions
22
Q

Polychromatophilic erythroblast

A
  • morphology- size of cell continues to decrease
  • nucleus- smaller than that of basophilic erythroblast, further condensation of chromatin, nucleolus will be lost
  • cytoplasm-gradual shift from intense basophilia to intense acidophilia- due to increase in amount of hemoglobin and decreases in number of polysomes- hemoglobin binds to anionic dye eosin, RNA of ribosomes binds cationic dye methylene blue, cytoplasm has a double staining reaction
  • lasts about 3 days
  • capable of 3-4 mitotic divisions
23
Q

Normoblast

A
  • no longer capable of mitosis
  • morphology:
  • smaller than polychromatophilic erythroblast
  • nucleus-smaller than that of polychromatophilic erythroblast, totally heterochromatic
  • cytoplasm-faintly polychromatophilic, mostly pink with a hint a blue, due to presence of lots of hemoglobin and a few remaining polyribosomes
24
Q

Reticulocytes

A
  • 80% of normoblasts
  • extrude nucleus (unequal cytokinesis)
  • cytoplasm contains a few polyribosomes- residual ribosomal RNA can be stained with brilliant cresyl blue
  • can remain briefly in bone marrow
  • may be released into peripheral circulation- after 1 day in circulation residual RNA is lost, cell becomes mature red blood cell
  • reticulocytes make up about 1% of total number of red blood cells
  • normoblast-reticulocyte period lasts 3 days
25
Q

Orthochromatic erythroblasts

A
  • 20% of normoblasts become this
  • lose residual RNA before they extrude nuclei
  • small heterochromatic nucleus
  • bright eosinophilic cytoplasm
  • not normally released into peripheral circulation
26
Q

Kinetics of erythrocyte production

A
  • process takes from 8-9 days
  • most of the time is spent in bone marrow
  • 1-2 days as basophilic erythroblast
  • 3 days as polychromatophilic erythroblast
  • 3 days as normoblast-reticulocyte
  • 1 day for reticulocyte-erythrocyte transition
27
Q

Distribution of erythrocytes

A
  • number of circulating mature red blood cells is about 20X the number of immature forms of bone marrow
  • ready reserve:
  • located in red bone marrow
  • reticulocytes that slightly outnumber circulating reticulocytes
28
Q

Erythropoietin

A
  • glycoprotein hormone
  • synthesized in kidney cortex (endothelial cells of peritubular capillary plexus
  • increases rate of mitosis in developing red blood cells- blasts, basophilic erythroblasts, polychromatophilic erythropoietin
  • increases RNA synthesis in developing rbcs
  • hypoxia stimulates the synthesis of erythropoietin (hemorrhage, hemolysis, high altitude, compromise of pulmonary function)
29
Q

Reticular cells (adventitial cells)

A
  • morphology- large cells with many cytoplasmic processes
  • contain lots of ingested material in their cytoplasm
  • large pale staining nucleus

erythroblastic islands- polychromatophilic erythroblasts clustered around reticular cells

  • play a trophic role in the maturation of erythrocytes- supply nutrients and growth factors to developing rbcs
  • phagocytose extruded normoblast nuclei
30
Q

Plasma cells

A
  • can be observed in bone marrow smears
  • basophilic cytoplasm
  • negative image of Golgi apparatus
  • eccentrically placed nucleus
  • clock face distribution of chromatin
31
Q

Megakaryocyte Differentiation

A
  • cell enlargement
  • lobulation of nucleus
  • increase in level of ploidy (32-64 n)
  • shift in cytoplasmic basophilia to acidophilia
  • accumulation of azurophilic cytoplasmic granules
  • formation of platelet demarcation channels
32
Q

Megakaryoblast

A
  • large cell 40-50um in diameter
  • large oval or spherical nucleus (polyploid)
  • homogenous basophilic cytoplasm
33
Q

Megakaryocyte

A
  • even larger cell (up to 150um in diameter)
  • lobulated nucleus
  • increase in ploidy up to 32-64n (endomitosis)
  • cytoplasm becomes eosinophilic
  • azurophilic granules appear in cytoplasm
  • invaginations of plasma membrane develop throughout cytoplasm- forms demarcation channels, results in partitioning of cytoplasmic fragments to form platelets, platelets enter discontinuous sinusoids in bone marrow
  • contain a functional repertoire of mRNAs
  • platelets may be able to produce functional progeny?
34
Q

Model of platelet production

A
  • pseudopod formation
  • pseudopods elongate forming proplatelets
  • platelets released from ends of proplatelets
  • demarcation channels are a membrane reservoir
35
Q

Kinetics of platelet formation

A
  • megakaryocyte maturation takes 4-5 days in humans
  • platelets then circulate for about 10 days
  • destroyed in spleen and liver
36
Q

Lymphocyte differentiation

A
  • cell size decrease, chromatin becomes condensed, nucleoli becomes less visible, lymphocyte subsets acquire distinctive cell surface receptors
  • lymphoblasts reside in bone marrow
  • some of their progeny migrate to the thymus- will then acquire characteristics of T lymphocytes- after they will populate lymphoid organs- lymph nodes, spleen, tonsils
  • some progeny remain in bone marrow for a while, they begin to differentiate to B cells, leave bone marrow and migrate to peripheral lymphoid organs where they complete their differentitations- lymph nodes, spleen, tonsils
37
Q

Monocytes

A
  • develop from blasts within red bone marrow
  • small azurophilic granules appear in the cytoplasm-smaller than primary granules at neutrophilic promyelocyte, they are lysosomes- contain alpha-napthyl acetate esterase
  • nuclei assume unusal shapes
  • formation in bone marrow takes 2-3 days
  • remain in peripheral circulation for 1-2 days
  • migrate to tissues and become histiocytes (macrophages)
  • may function as tissue macrophages for 1-3 months

Microscopic Anatomy (7 decks)

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