UNIT 4. ERYTHROCYTE PRODUCTION

Mature erythrocytes

nonnucleated, biconcave discs with a central pallor that occupies one-third of the cell

120 days

erythrocytes life span

Oxygen transport: transports or carries oxygen from the lungs to the tissues where oxygen is released

erythrocytes main function

• CO2 transport: transports carbon dioxide from the tissues to the lungs

• buffers the pH of the blood

erythrocytes 2ndary function

• IL 3

• GM-CSF

• Kit Ligand

BFU-E matures into CFU-E under the influence of what factors/substance?

Erythropoietin

CFU-E matures into RBC Precursor Cells (Pronormoblast) under the influence of _

Pluripotent HSC → Multipotent Progenitors (MPP) → Common Myeloid Progenitor (CMP) → BFU-E → CFU-E → RBC Precursor cells → Mature RBC

Enumerate the sequence of erythropoiesis

• Burst-Forming Unit-Erythroid

• Colony-Forming Unit-Erythroid

Enumerate the Erythroid Progenitors

BFU-E

• earliest committed progenitor of the erythrocytic lineage

• gives rise to large colonies

CFU-E

erythroid progenitors that gives rise to smaller colonies

1 week

BFU-E → CFU-E takes up to _

1 week

CFU-E → pronormoblast takes up to _

6 to 7 days

Pronormoblast → mature RBC takes up to _

18-21 days

BFU-E → mature RBC takes up to a total of _

CFU-E

more sensitive to EPO because of its many EPOR in its surface

EPO

major hormone for stimulating RBC production

targets cells containing EPOR

cell division (proliferation) and maturation

Normoblastic proliferation occurs through _ and _

Pronormoblast → Basophilic normoblast → Polychromatic normoblast → Orthochromic normoblast → Polychromatic erythrocyte

Enumerate the sequence of ERYTHROID PRECURSORS

Erythrocytes

term used for mature RBCs and erythroid cells without nucleus

Erythroblasts/Normoblasts

term used for immature RBCs; nucleated precursors in the BM; developing nucleated cells with normal appearance

1. Pronormoblast

2. Basophilic normoblast

3. Polychromatic (polychromatophilic) normoblast

4. Orthochromic normoblast

5. Polychromatic (polychromatophilic) erythrocyte

6. Erythrocyte

Enumerate the Erythroid precursors in sequence using the NORMOBLASTIC NOMENCLATURE

1. Rubriblast

2. Prorubricyte

3. Rubricyte

4. Metarubricyte

5. Polychromatic (polychromatophilic) erythrocyte

6. Erythrocyte

Enumerate the Erythroid precursors in sequence using the RUBRIBLASTIC NOMENCLATURE

1. Proerythroblast

2. Basophilic erythroblast

3. Polychromatic (polychromatophilic) erythroblast

4. Orthochromic erythroblast

5. Polychromatic (polychromatophilic) erythrocyte

6. Erythrocyte

Enumerate the Erythroid precursors in sequence using the ERYTHROBLASTIC NOMENCLATURE

Polychromatic normoblast

the last stage capable of cell division (proliferation)

“polychromatophilic erythrocyte”

“diffusely basophilic erythrocyte

These are terms sometimes used for reticulocytes (peripheral blood film)

• Diameter of the cell decreases

• Diameter of nucleus decreases more rapidly than the cell ; N:C ratio decreases

• Nuclear chromatin pattern → coarser, clumped, condensed (raspberry-like appearance)

• Nucleoli disappear → cessation of protein synthesis

• Cytoplasm changes from blue to gray-blue (Basophilic) to salmon pink (Acidophilic/Eosinophilic)

ENUMERATE CRITERIA USED IN THE IDENTIFICATION OF ERYTHROID PRECURSORS

raspberry-like appearance

As erythroid precursors mature, their nuclear chromatin pattern become coarser, clumped, condensed, resembling a _

protein synthesis

Disappearance of nucleoli is attributed to the cessation of _

condensation of nuclear chromatin

Decrease in nuclear size and the N:C ratio is attributed to the _

Blueness or basophilia

due to its acidic components which attract basic stain (methylene blue)

Directly proportional

↑ Basophila ↑ Ribosomal RNA

Relationship between basophilia and the amount of ribosomal RNA, ribosomes, and other organelles

Pinkness or eosinophilia/acidophilia

due to its basic components which attract acid stain (eosin)

Directly proportional

↑ Eosinophila ↑ Hemoglobin production

Relationship between Eosinophila and Hgb production

Rubriblast (Pronormoblast)

the earliest recognizable erythroid precursor

12-19 µm (largest)

Rubriblast (Pronormoblast) size

8:1

Rubriblast (Pronormoblast) N:C ratio

Rubriblast (Pronormoblast)

• Contains 1 or 2 nucleoli

• Large, round nucleus

Rubriblast (Pronormoblast)

Chromatin is purple red and has a fine pattern / open

Rubriblast (Pronormoblast)

• Deep blue cytoplasm (due to ribosomes-RNA activity)

• without granules

Rubriblast (Pronormoblast)

High RNA activity (needed for production of CHONs required for Hgb synthesis)

Rubriblast (Pronormoblast)

• Globin production & Heme synthesis begins

Rubriblast (Pronormoblast)

12-17 µm

Prorubricyte (Basophilic Normoblast) size

6:1

Prorubricyte (Basophilic Normoblast) N:C ratio

Prorubricyte (Basophilic Normoblast)

• Nucleoli may be present in the early stage but disappears later

Prorubricyte (Basophilic Normoblast)

• Nuclear chromatin is deep purple red and begins to condense → “Patially clumped/condensed”

Prorubricyte (Basophilic Normoblast)

• Deeper, richer blue cytoplasm = Protein synthesis begins

Prorubricyte (Basophilic Normoblast)

• Start of hemoglobin synthesis (Hgb pigmentation not yet evident)

Eosinophila is being masked by the high amount of ribosomal RNA & ribosomes in the cytoplasm

Why is Hgb pigmentation (eosinphilia) not yet evident in Prorubricytes even though Hgb synthesis have alr started?

Prorubricyte has a coarser chromatin and absence of nucleoli

Most helpful criteria in comparing Prorubricyte with rubriblast

Prorubricyte (Basophilic Normoblast)

11-15 µm

Rubricyte (Polychromatophilic normoblast) size

4:1

Rubricyte (Polychromatophilic normoblast) N:C ratio

Rubricyte (Polychromatophilic normoblast)

• No nucleoli are present

• Increased clumping of the chromatin → “Moderately clumped/condensed”

murky gray-blue from Pink (Hgb) + Blue (RNA)

Rubricyte (Polychromatophilic normoblast) cytoplasm color

Rubricyte (Polychromatophilic normoblast)

• Hemoglobin synthesis increases (Hgb pigmentation becomes evident)

Rubricyte (Polychromatophilic normoblast)

• Last stage capable of mitosis

• Progressive ↓ in DNA synthesis

Rubricyte (Polychromatophilic normoblast)

Metarubricyte (Orthochromic normoblast or nucleated RBC/NRBC)

8-12 µm

Metarubricyte (Orthochromic normoblast) size

1:2

Metarubricyte (Orthochromic normoblast) N:C ratio

Metarubricyte (Orthochromic normoblast)

• Chromatin pattern is tightly/completely condensed → Pyknotic nucleus

Pyknotic nucleus

dense/compact mass of degenerated chromatin is called _

Metarubricyte (Orthochromic normoblast)

• nucleus becomes inactive

• synthetic activity and cell division ability is lost

Metarubricyte (Orthochromic normoblast)

• where nucleus explusion/extrusion occurs

Metarubricyte (Orthochromic normoblast)

Reddish pink with slightly bluish color of cytplasm

Metarubricyte (Orthochromic normoblast)

• Last nucleated stage

• Hgb synthesis continues

Metarubricyte (Orthochromic normoblast)

• Hgb synthesis is nearing completion

• RNA begins to degrade

vimentin

Nucleus expulsion is initiated when _, a protein which hold organelles in proper location in the cytoplasm, is lost by the cell.

myosin

In the pinching process of nucleus expulsion, _ contracts to push the nucleus outside the cell.

Pyrenocyte

pyknotic/enveloped extruded nucleus is called _

Phosphatidylserine (phospholipid)

the pyrenocyte is covered by the cell membrane which contains _ acting as “eat me flag”

Macrophages

bone marrow

_ in the _ engulfs the pyrenocyte

7-10 µm

Reticulocyte (Polychromatophilic erythrocyte) size

No N:C ratio because it is anucleate

Reticulocyte (Polychromatophilic erythrocyte) N:C ratio

Reticulocyte (Polychromatophilic erythrocyte)

• Cell is anuclear

• Diffuse reticulum

Reticulocyte (Polychromatophilic erythrocyte)

• Various degrees of polychromasia (mixed pink and blue staining)

• pink is more dominant with bluish tints

Polychromatophelia

Increased Polychromatic erythrocytes in the peripheral blood

Reticulocyte (Polychromatophilic erythrocyte)

• End-stage of Hgb synthesis

Reticulocyte (Polychromatophilic erythrocyte)

residual RNA & ribosomes are completely lost at the end of this stage

endoribonuclease

In reticulocytes, _ digests the ribosomes

Diffusely Basophilic Erythrocyte

term used for Polychromatophilic erythrocyte when bluish tint is scattered/spread in the cytoplasm

Wright’s stain

Diffusely Basophilic Erythrocyte is demonstrated by _

Reticulocyte

term used for Polychromatophilic erythrocyte when bluish tint appear as small, blue, granulofilamentous strands due to the precipitation of residual RNA with the stain

reticulum

small blue strands found in reticulocytes are called _

Supravital stain

Reticulocytes are demonstrated using _, which stains cells alive

• New Methylene Blue (NMB)

• Brilliant Cresyl Blue (BCB)

Examples of Supravital Stains

Punctate basophila

occurs when residual RNA appears as distinct blue dots all over the cell’s cytoplasm

Wright’s stain

Punctate basophila is demonstrated using _

lead poisoning

Punctate basophila is manifested in events like _

1-2 or 2-3 days

Reticulocyte (Polychromatophilic erythrocyte) resides in the BM for __ prior to its release in PB

spleen

After residing in the BM, reticulocytes circulate in the _ to undergo needed changes before their eventual release to the PB

pitting & membrane polishing → BICONCAVE DISCOID MATURE RBC

What happens to the reticulocytes as their circulate in the spleen

1 day

Reticulocyte (Polychromatophilic erythrocyte) stays in the PB for about _ before becoming mature RBC

Erythrocyte

6-8 µm

Erythrocyte size

Erythrocyte

• Salmon-pink with central pale area cytoplasm

Erythrocyte

• cannot divide (anucleate

• No mitochondria

• Biconcave disc (discocyte)

Hemoglobin

main component of erythrocytes

oxygen-carrying component

Anaerobic glycolysis (Embden–Meyerhof–Parnas (EMP) Pathway);

plasma

Since erythrocytes have no mitochondria, energy production is done through _, which uses glucose from _