Module 5: Hemapoiesis (Erythroid Series)

Erythropoiesis

a complex, regulated process formaintaining adequate numbers of erythrocytes in theperipheral blood

ERYTHROPOIESIS

• begins with the development of primitive erythrocytes in the embryonic yolk sac

• continues in extramedullary sites, which primarily includes liver and the spleen in the developing fetus

• ultimately located in the red bone marrow during late fetal development, childhood and adult life

Erythropoietin (EPO)

Glycoprotein hormone produced primarily by the kidneys

Liver

Where is EPO produced? It is also the primary source of EPO in the unborn.

10-15%

How much EPO does liver produces?

stimulate erythropoiesis

main function of erythropoietin

Inversely Related

Relation of blood levels of EPO in the body to the degree of tissue oxygenation?

↑ Levels of EPO

↓ Tissue Oxygenation

Tissue hypoxia

produces a dramatic increase in EPO production

• Prevent apoptosis of erythroid progenitors

• Induce hemoglobin synthesis

Other functions of Erythropoietin

Bust Forming Unit-Erythroid (BFU-E)

Earliest identifiable colony of RBCs, which contain only a few receptors for EPO

Colony Forming Unit-Erythroid

CFU-E

influences CFU-E

• Interleukin-3 (IL-3)

• GM-CSF

• Monocytes

• Thrombopoietin (TPO)

• KIT ligand

Pronormoblasts

the earliest visually recognized erythrocyte precursor in the bone marrow

BFU-E

earliest visually recognized erythrocyte precursor in the bone marrow

1 week

BFU-E → CFU-E

another 1 week

CFU-E → Pronormoblast

6-7 days

Pronormoblast → Mature RBC

18-21 days

BFU-E → mature RBC

Erythrocytes

RBCs are formally called?

Erythroblasts or Normoblasts

the nucleated precursors in the bone marrow

Normoblastic terminology

nomenclature for naming erythroid precursors used in US

Rubriblastic terminology

nomenclature for naming erythroid precursors used in local Philippine setting

3 known nomenclatures for naming erythroid precursors

• Normoblastic terminology

• Rubriblastic terminology

• Erythroblastic terminology

Polychromatic erythrocytes

are called reticulocytes when observed with vital stains

Criteria used in the Identification of Erythroid Precursors

• Nuclear chromatin pattern

• Nuclear diameter

• Nucleus to Cytoplasm (N:C) ratio

• Presence or absence of nucleoli

• Cytoplasmic color

Maturation Process

1 Pronormoblast (Rubriblast / Proerythroblast)

2 Basophilic Normoblast (Prorubricyte)

3 Polychromatophilic Normoblast (Rubricyte)

4 Orthochromic Normoblast (Metarubricyte)

5 Polychromatophilic Erythrocyte (Reticulocyte)

6 Erythrocyte (Mature Erythrocyte)

Pronormoblast

Globin chain production begins.

Globin

is a component of hemoglobin

purple-red, open chromatin

is the most reliable nuclear indicator that the cell is a rubriblast

8:1

N:C ratio of pronormoblast

dark blue

Pronormoblast cytoplasm

bone marrow

Pronormoblast is seen in?

6:1

N:C ratio of Basophilic Normoblast

deep blue

Basophilic Normoblast cytoplasm

Polychromatophilic Normoblast

Only very slightly larger than the mature erythrocyte

4:1 to 1:1 (late stage)

N:C ratio range of Polychromatophilic Normoblast

murky gray blue

Polychromatophilic Normoblast cytoplasm

about 30 hours

How long does Polychomatophilic Normoblast lasts?

Orthochromic Normoblast

Cell diameter is nearly the same as the mature RBC

Orthochromic Normoblast - 1:2

Nucleus is completely condensed. N:C ratio of this erythropoietin?

increasing pink color

Ortochromic Normoblast cytoplasm

bone marrow and peripheral blood

Where is Metarubicyte seen?

aprox. 48 hours in the bone marrow

How long does Ortochromatic Erythroblast lasts?

Polychromatophilic Erythrocyte

• Slightly larger than mature RBC

• Residual mRNA and ribosomes can be seen with

  vital stains

• Irregular shaped

1 day or more

How long is Reticulocyte seen in bone marrow?

1 to 2 days

How long is Reticulocyte seen in peripheral blood?

0

number of nucleus in Polychromatophilic Erythrocyte

predominantly pink

Reticulocyte cytoplasm

Erythrocyte

• Remain active in the circulation for about 120 days

• Main function is oxygen delivery to the different tissues of the body through the action of hemoglobin

Proerythroblast

Erythroblastic name for Pronormoblast

Basophilic erythroblast

Erythroblastic name for Basophilic normoblast

Polychromatic erythroblast

Erythroblastic name for Polychromatic normoblast

Ortochromic erythroblast

Erythroblastic name for Orthochromic normoblast

Rubriblast

Rubriblastic name for Pronormoblast

Prorubricyte

Rubriblastic name for Basophilic normoblast

Metarubricyte

Rubriblastic name for Orthochromic normoblast

None

Nucleus in Erythrocyte

salmon pink with a central area of pallor (about 1/3 the diameter of RBC)

Erythrocyte cytoplasm

7-8 um

shape of Erythrocyte

1.5-2.5 um

thickness of Erythrocyte

peripheral blood

Where is Erythrocyte seen?

about 30 hours

How long does Erythrocyte lasts?

Metarubricyte

Identify the cell.

Prorubicyte

Identify the cell.

Rubriblast

Identify the cell.

Rubricyte

Identify the cell.

no mitosis

• Orthochromic Normoblast

• Polychromatophilic Erythrocyte

• Erythrocyte

undergo mitosis

• Pronormoblast

• Polychromatophilic Normoblast