Histology - Hematopoiesis

Front 1

General Cell Progression in Hematopoiesis:

Back 1

1.) Stem Cells
-self-renewing
-low mitotic activity
-eg: Myeloid Multipotential Cells

2.) Progenitor Cells
-self-renewing
-high mitotic activity
-eg: Erythrocyte-Colony-Forming-Cell (ECFC)

3.) Precursor Cells
-not self-renewing
-high mitotic activity
-beginning of morphological distinctions (committed)
-eg: Erythroblast

4.) Mature Cells
-no mitotic activity
-clear morphological distinction
-eg: Erythrocyte

Front 2

Bone Marrow Components

Back 2

Bone Marrow Components:

-Stroma
-Fibroblast-like Reticular Cells
-Sinusoids (like capillaries, but bigger)

Front 3

Red vs Yellow Bone Marrow

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Bone Marrow:

Red: Hematopoietic
Yellow: Fat (tends to be hollow center of long bones as age)

*Yellow can convert back to Red if needed/stimulated
*Hematopoiesis takes place in Liver in Fetus

Front 4

Red Blood Cell Development

Back 4

Red Blood Cell Development:
Changes:
a.) Size Decreases
b.) Nucleus compacted & expelled
c.) Plasma shifts basophilic to acidophilic

1.) Proerythroblast

2.) Basophilic Erythroblast
-polyribosomes synthesizing protein give basophilic appearnace

3.) Polychromatophilic Erythroblast
-Hemoglobin rising, shifting acidophilic

4.) Orthochromatophilic Erythroblast
-lots of Hemoglobin, redder
-dense heterochromatin
-nucleus expelled

5.) Polychromatophilic Erythrocyte (Reticulocyte)
-no nucleus
-mostly red

6.) Erythrocyte
-drops RNA losing all basophilic
-acidophilic (red) appearance

Front 5

Reticulocyte

Back 5

Reticulocyte:

-precursor to Erythrocyte
-retains some remnant, polyribosome or DNA (argued)
-some released into circulation

Reticulocytosis - increased Reticulocytes marks increased hematopoiesis

Front 6

Leukopoiesis

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Leukopoiesis:

-Stimulated by "Colony Stimulating Factors" (interleukins & interferons)
-released by WBCs themselves during infection to increase WBC levels

-Azurophilic, or non-specific, granules appear early on in development, before specific granules (in granulocytes)

-Azurophilic Granuldes = non-specific granules = LYSOSOMES

Front 7

Granulopoiesis vs Erythropoiesis

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Granulopoiesis vs Erythropoiesis:

Distinguish by presence or lack of granules, respectively

Front 8

Thrombopoiesis

Back 8

Thrombopoiesis:

-Megakaryocyte in bone marrow has extensions into sinusoids, releases fragments which become thrombocytes

-highly lobulated nucleus
-can see "platelet demarcation channels" in megakaryocyte, debated function
-used to think platelets broke off here, seems unlikely now