Normal Hematopoiesis Flashcards by Kyra Porter

tissues of the hematopoietic system

-bone marrow and all blood corpuscles
-liver
-spleen
-lymph nodes
-thymus

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bone marrow

*hollow spaces of bones filled with all blood cell precursors

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bone marrow cellularity & aging

*infancy: cellularity is 100%
*cellularity decreases by 10% with each decade of life
*around age 70-80, cellularity remains at 20-30%
*general rule of thumb for bone marrow cellularity: 100 - age of patient

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normal production of bone marrow

*normal myeloid to erythroid ratio is 3:1
*controlled growth with increase in activity based upon demand [infection, low tissue oxygenation, etc]
*ACTIVITY IS DECREASED WHEN DEMAND IS MET (return to steady state bone marrow production)
*mediated by growth factors
*increase in production results in greater numbers of mature cells and some young cells, but no immature cells are released

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stromal matrix of bone marrow

*stromal cells [fibroblasts, fat cells, endothelial cells]
*adhesion molecules
*growth factors

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hematopoiesis during embryogenesis

*hematopoiesis begins early (week 3)
*mesenchymal cells either become endothelial cells or blood cells

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site of hematopoiesis in the first 6 weeks of gestation

yolk sac

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site of hematopoiesis 6-18 weeks of gestation

liver

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site of hematopoiesis 18-30 weeks of gestation

liver and spleen

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site of hematopoiesis 30 weeks of gestation to birth to 8 week old infant

liver, spleen, and bone marrow

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site of hematopoiesis > 10 weeks postnatal

bone marrow ONLY

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normal erythropoiesis: stages of red cell maturation

pronormoblast
basophilic normoblast
polychromatophilic normoblast
orthochromatic normoblast
reticulocyte
mature red blood cell

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normal erythropoiesis: how does the CELL SIZE change during maturation from a pronormoblast to a mature RBC?

cell size DECREASES with maturation

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normal erythropoiesis: how does the NUCLEUS change during maturation from a pronormoblast to a mature RBC?

*nucleus is always ROUND
*chromatin condenses with maturation
*nucleus:cytoplasm ratio DECREASES with maturation
*ultimately, the nucleus disappears

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normal erythropoiesis: how does the CYTOPLASM change during maturation from a pronormoblast to a mature RBC?

*basophilia (blue cytoplasm) = immaturity
*magenta = as maturation occurs and hemoglobin accumulates
*no granules

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characteristics of a mature RBC

*no nucleus
*no cytoplasmic organelles
*no protein or lipid synthesis
*no oxidative phosphorylation

basic functions of a mature RBC

*picks up oxygen from the lungs
*delivers oxygen to tissues
*picks up CO2 from the tissues
*delivers CO2 to the lungs

mature RBC: shape

*biconcave disk shape → large surface area → good for gas exchange
*highly deformable; allows changes in size (8 microns in a large vein to 2 microns in a capillary)
*proper RBC function (due to proper shape) is essential for the function of the rest of the body

categories of leukocytes (WBCs)

granulocytes [neutrophils, eosinophils, basophils]
lymphocytes [T cells, B cells, natural killer cells]
monocytes [tissue macrophages]

alternative names for neutrophils

*polys
*PMNs (polymorphonuclear neutrophil)
*Segs (segmented neutrophils)
*CHARACTERIZED BY NUCLEI WITH: 3-5 lobes separated by a thread

6 stages of neutrophil maturation

myeloblast
promyelocyte
myelocyte
metamyelocyte
band
neutrophil

functions of neutrophils

*help fight infection, esp bacterial infections
*can phagocytize small particles:
-particle gets surrounded by pseudopods that fuse, forming a vacuole/phagosome
-granules fuse with phagosome
-contents enter, dropping pH to 4.0
-acidic environment plus additional enzymes result in killing and digestion of bacteria

lifespan of neutrophils

*live for 6-7 hours in the blood
*live for 1-4 days in tissue

eosinophils - overview

*bi-lobed nucleus
*eosinophilic (pink, juicy) granules
*PARASITIC INFECTIONS, allergic reactions, vasculitis, some hematologic malignancies

basophils - overview

*basophilic (dark purple/blue) granules *role in allergic disorders: -IgE receptors -allergen binds to IgE -release histamine *increased in myeloproliferative disorders

monocytes - overview

*large, kidney-shaped nucleus; extensive "frosted glass" cytoplasm *circulate in the bloodstream for only 24 hours *then, go into tissues to become MACROPHAGES or dendritic cells *ingest fungi, mycobacteria, and play a role in battling pyogenic bacteria

development of lymphocytes

*produced in bone marrow *migrate to other sites of the body to mature and acquire specific properties: -T cells: mature in thymus; helper and suppressor cells -B cells: produce antibodies against foreign antigens {plasma cells) -NK cells: large granular lymphocytes

characteristics of lymphocytes

*round, densely staining nucleus with very little cytoplasm *typically do NOT have granules *nucleus is about the same size as a RBC *life span = years *peripheral blood: -70% T cells -25% B cells -<5% NK cells -NO plasma cells

antigens expressed on B cells

*CD10 *CD19 *CD20 *CD79 *sIg kappa/lambda

antigens expressed on NK cells

*CD16 *CD56

antigens expressed on T cells

*CD3 *CD4 *CD5 *CD7 *CD8

platelets - overview

*megakaryocytes are multinucleated precursors of platelets -largest cells in the body -do not circulate (filtered out by lung microvasculature) *no intermediate maturation stages (little bits of the cytoplasm pinch off to form platelets; 1 megakaryocyte can create a bunch of platelets)

spleen - general functions

*"lymph node on steroids": largest collection of lymphoid tissue in a person (spleen is full of lymphocytes) *help filter the blood to remove: -pathogens -senescent or abnormal blood cells *lymph nodes filter lymph; SPLEEN FILTERS BLOOD

white pulp of spleen - function

*lymphoid nodules within the red pulp *~25% of lymphocytes in the body are in the spleen *T cells form PALS (periarterial lymphatic arteries) around the central arterioles *B cells comprise the majority of the lymphoid nodule *antigen-presenting cells (dendritic cells)

red pulp of spleen - function

*red = rich in blood *composed of SINUSOIDS and SPLENIC CORDS called BILIROTH'S CORDS -cords are dead ends; cells are trapped if they can't squeeze through -during periods of extensive red cell damage and splenic activity, blood may enter the spleen but be unable to exit (sequestration) *many monocyte-macrophages (monos/macs are most active here than anywhere else in the body)