erythrocyte production

1. Erythrocyte
Production and
Destruction
HEMATOLOGY 1
Prepared by:
LGGRMT

2. Function: to carry oxygen from the lung to the tissues, where the oxygen is
released. (attachment of O₂ to hemoglobin)
Erythroblasts
● nucleated precursors in the bone marrow.
● “Normoblasts” refers to developing nucleated cells (i.e., blasts) with
normal appearance.

3. Criteria Used in Identification of the Erythroid
Precursors
● modified Romanowsky stain: Wright or Wright-Giemsa
a. Maturation: Chromatic and Nucleus
b. Nuclear chromatin pattern: texture, density, homogeneity
c. nuclear diameter
d. nucleus:cytoplasm (N:C) ratio
e. presence or absence of nucleoli
f. Cytoplasmic color

4. ● As RBCs mature, several general trends affect their appearance.
1. The overall diameter of the cell decreases.
2. The diameter of the nucleus decreases more rapidly than does the size of
the cell. As a result, the N:C ratio also decreases.
3. The nuclear chromatin pattern becomes coarser, clumped, and
condensed. It becomes even coarser and more clumped as the cell
matures, developing a raspberry-like appearance, in which the dark
staining of the chromatin is distinct from the almost white appearance of
the parachromatin. This chromatin/parachromatin distinction is more
dramatic than in other cell lines. Ultimately, the nucleus becomes quite
condensed, with no parachromatin evident at all, and the nucleus is said to
be pyknotic.
4. Nucleoli disappear.

5. 5. The cytoplasm changes from blue to gray-blue to salmon pink.
Blueness or basophilia is due to acidic components that attract the
basic stain, such as methylene blue

6. MATURATION PROCESS
❖ Erythroid Progenitors
a. burst-forming unit–erythroid (BFU-E)
b. colony-forming unit–erythroid (CFU-E)
❖ Erythroid Precursors
1. Pronormoblast (Proerythroblast or Rubriblast)
2. Basophilic normoblast (Basophilic Erythroblast or Prorubricyte)
3. Polychromatic (polychromatophilic) normoblast (Polychromatic
Erythroblast or Rubricyte)
4. Orthochromic normoblast (Orthochromic Erythroblast or
Metarubricyte)
5. Polychromatic (polychromatophilic) erythrocyte (Diffusely Basophilic
Erythrocyte or Reticulocyte
6. Erythrocyte

7. Pronormoblast (Rubriblast)
REFERENCE INTERVAL
Bone Marrow: 1%
Peripheral Blood: 0%
The pronormoblast is present only in
the bone marrow in healthy states.

8. NUCLEUS:
● The nucleus takes up much of the cell (N:C ratio of 8:1).
● The nucleus is round to oval, containing 1 or 2 nucleoli.
● The purple red chromatin is open and contains few, if any, fine clumps.
● Size: 12 to 20 μm
CYTOPLASM:
● The cytoplasm is dark blue because of the concentration of ribosomes.
The Golgi complex may be visible
● Pronormoblasts may show small tufts of irregular cytoplasm along the
periphery of the membrane.

9. DIVISION:
● The pronormoblast undergoes mitosis and gives rise to two daughter
pronormoblasts.
CELLULAR ACTIVITY:
● The pronormoblast begins to accumulate the components necessary
for hemoglobin production.
● The proteins and enzymes necessary for iron uptake and protoporphyrin
synthesis are produced.
● Globin production begins
LENGTH OF TIME IN THIS STAGE:
● This stage lasts slightly more than 24 hours.

10. Basophilic Normoblast (Prorubricyte)
REFERENCE INTERVAL:
Bone Marrow: 1% to 4%
Peripheral Blood: 0%
The polychromatic normoblast is present
only in the bone marrow in healthy states.

11. NUCLEUS:
● The chromatin begins to condense, revealing clumps along the periphery
of the nuclear membrane and a few in the interior.
● N:C ratio decreases to about 6:1.
● The chromatin stains deep purple-red.
● SIZE: 10 to 15 μm
● Nucleoli: 0 to 1
CYTOPLASM:
● When stained, the cytoplasm may be a deeper, richer blue than in the
pronormoblast—hence the name basophilic for this stage.

12. DIVISION:
● The basophilic normoblast undergoes mitosis, giving rise to two daughter
cells.
CELLULAR ACTIVITY:
● Detectable hemoglobin synthesis occurs, but the many cytoplasmic
organelles, including ribosomes and a substantial amount of messenger
ribonucleic acid (RNA; chiefly for hemoglobin production), completely mask
the minute amount of hemoglobin pigmentation.
LENGTH OF TIME IN THIS STAGE:
● lasts slightly more than 24 hours.

13. Polychromatic (Polychromatophilic) Normoblast (Rubricyte)
The polychromatic normoblast is present
only in the bone marrow in healthy
states.
REFERENCE INTERVAL:
Bone Marrow: 10% to 20%
Peripheral Blood: 0%

14. NUCLEUS:
● The chromatin pattern varies during this stage of development, showing
some openness early in the stage but becoming condensed by the end.
● N:C ratio decreases from 4:1 to about 1:1 by the end of the stage.
● Notably, no nucleoli are present.
CYTOPLASM:
● This is the first stage in which the pink color associated with stained
hemoglobin can be seen.
● The color produced is a mixture of pink and blue, resulting in a
● murky gray-blue.
● The stage’s name refers to this combination of multiple colors, because
polychromatophilic means “many color loving.”
● “Gray-blue as a result of hemoglobinization”

15. DIVISION:
● This is the last stage in which the cell is capable of undergoing mitosis.
CELLULAR ACTIVITY:
● Hemoglobin synthesis increases, and the accumulation begins to be visible
in the color of the cytoplasm.
● Cellular organelles are still present, particularly ribosomes, which contribute
a blue aspect to the cytoplasm.
● The progressive condensation of the nucleus and disappearance of nucleoli
are evidence of progressive decline in transcription of deoxyribonucleic acid
(DNA).
LENGTH OF TIME IN THIS STAGE:
● lasts approximately 30 hours.

16. Orthochromic Normoblast (Metarubricyte)
REFERENCE INTERVAL:
Bone Marrow: 5% to 10%
Peripheral Blood: 0%
The orthochromic normoblast is
present only in the bone marrow in
healthy states.

17. NUCLEUS:
● The nucleus is completely condensed (i.e., pyknotic) or nearly.
● N:C ratio is low or approximately 1:2.
● SIZE: 8 to 10 μm
CYTOPLASM:
● The increase in the salmon-pink color of the cytoplasm reflects nearly
complete hemoglobin production.
● The residual ribosomes react with the basic component of the stain and
contribute a slightly bluish hue to the cell, but that fades toward the end
of the stage as the organelles are degraded.
●

18. DIVISION:
● The orthochromic normoblast is not capable of division due to the
condensation of the chromatin
CELLULAR ACTIVITY:
● Hemoglobin production continues on the remaining ribosomes using
messenger RNA produced earlier.
● The nucleus is ejected from the cell. The nucleus moves to the cell
membrane and into a pseudopod-like projection.
● Loss of vimentin, a protein responsible for holding organelles in proper
location in the cytoplasm.
LENGTH OF TIME IN THIS STAGE:
● lasts approximately 48 hours

19. Polychromatic (Polychromatophilic) Erythrocyte or Reticulocyte
The polychromatic erythrocyte
resides in the bone marrow for 1 day
or longer and then moves into the
peripheral blood for about 1 day
before reaching maturity.
During the first several days after
exiting the marrow, the
polychromatic erythrocyte is retained
in the spleen for pitting of inclusions
and membrane polishing by splenic
macrophages, which results in the
biconcave discoid mature RBC
REFERENCE INTERVAL:
Bone Marrow: 1%
Peripheral Blood: 0.5% to 2.0%

20. Polychromatic (Polychromatophilic) Erythrocyte or Reticulocyte
NOTE:
When stained with supravital
stain (e.g., new methylene
blue), polychromatic
erythrocytes appear as
reticulocytes (contain
precipitated ribosomal
material)

21. NUCLEUS:
● no nucleus.
● Nucleoli: NA
● Chromatin: NA
● SIZE: 8 to 8.5 μm
● N:C RATIO: NA
CYTOPLASM:
● Color is slightly more blue/purple than the mature erythrocyte
● By the end of the polychromatic erythrocyte stage, the cell is the same
color as a mature RBC, salmon pink. It remains larger than a mature cell,
however. The shape of the cell is not the mature biconcave disc but is
irregular.

22. DIVISION:
● Lacking a nucleus, the polychromatic erythrocyte cannot divide.
CELLULAR ACTIVITY:
● The polychromatic erythrocyte completes production of hemoglobin from
residual messenger RNA using the remaining ribosomes.
● The cytoplasmic protein production machinery - dismantled.
● Endoribonuclease = digests the ribosomes.
● The acidic components that attract the basophilic stain decline

23. LENGTH OF TIME IN THIS STAGE:
● The cell typically remains a
polychromatic erythrocyte for
about 3 days, with the first 2 days
spent in the marrow and the third
spent in the peripheral blood,
although possibly sequestered in
the spleen.
● polychromatophilia is not readily evident in the polychromatic
erythrocytes on a normal peripheral blood film stained with Wright stain.
● small amount of residual ribosomal RNA =present (visualized with a vital
stain: new methylene blue.
● polychromatic erythrocyte (stained) = reticulocyte.

24. Erythrocyte
REFERENCE INTERVAL:
Bone Marrow: NA
Peripheral Blood: Predominant cell type
Mature RBCs remain
active in the circulation
for approximately 120
days.
Aging leads to their
removal by the spleen as
described subsequently.

25. NUCLEUS:
● No nucleus is present in mature RBCs.
● Nucleoli: NA
● Chromatin: NA
CYTOPLASM:
● The mature circulating erythrocyte is a biconcave disc measuring 7 to 8
mm in diameter
● Thickness = about 1.5 to 2.5 mm.
● On a stained blood film = salmon pink-staining cell with a central pale
area that corresponds to the concavity.
● The central pallor is about one third the diameter of the cell.

26. DIVISION:
● The erythrocyte cannot divide.
CELLULAR ACTIVITY:
● The mature erythrocyte delivers oxygen to tissues, releases
it, and returns to the lung to be reoxygenated.

28. ERYTHROKINETICS

29. ● describing the dynamics of RBC production and destruction.
● Erythron is the name given to the collection of all stages of
erythrocytes throughout the body.
● the developing precursors in the bone marrow and the circulating
erythrocytes in the peripheral
● blood and the vascular spaces within specific organs such as the
spleen.

30. Stimulus to Red Blood Cell Production
a. Hypoxia
- The primary oxygen-sensing system of the body is located in
peritubular fibroblasts of the kidney
- erythropoietin (EPO), the major stimulatory cytokine for RBCs
- When there is hemorrhage, increased RBC destruction, or other
factors that diminish the oxygen-carrying capacity of the blood the
production of EPO is ↑
b. Erythropoietin (EPO)
- thermostable, nondialyzable, glycoprotein hormone with a
molecular weight of 34 kD.
- carbohydrate unit that reacts specifically with RBC receptors and a
terminal sialic acid unit, which is necessary for biological activity in
vivo

31. Stimulus to Red Blood Cell Production
- true hormone, being produced at one location (the kidney) and
acting at a distant location (the bone marrow).
- a growth factor (or cytokine) that initiates an intracellular message
to the developing RBCs = signal transduction.
- EPO has three major effects:
1. Allowing early release of reticulocytes from the bone marrow
2. preventing apoptotic cell death.
3. reducing the time needed for cells to mature in the bone
marrow.
- Increased amounts of EPO in the urine are expected in most
patients with anemia, with the exception of patients with anemia
caused by renal disease.

32. C. Hormones:
- testosterone directly stimulates erythropoiesis,
which partially explains the higher hemoglobin
concentration in men than in women
- Pituitary and thyroid hormones

33. ERYTHROCYTE DESTRUCTION
● mature erythrocyte is unable to generate new proteins, such as
enzymes, so as its cellular functions decline, the cell ultimately
approaches death.
● has sufficient enzyme function to live 120 days
● RBCs lack mitochondria, they rely on glycolysis for production of
adenosine triphosphate (ATP).
● Aged RBCs, or senescent cells, cannot regenerate catabolized
enzymes because they lack a nucleus. The semipermeable
membrane becomes more permeable to water, so the cell swells and
becomes spherocytic and rigid. It becomes trapped in the splenic
sieve.

34. ● Extravascular or macrophage-mediated hemolysis accounts for most
normal RBC death
● The signals to macrophages that initiate RBC ingestion may include
binding of autologous IgG, expression of phosphatidylserine on the outer
membrane, cation balance changes, and CD47-thrombospondin 1 binding.
● Fragmentation or intravascular hemolysis results when mechanical factors
rupture the cell membrane while the cell is in the peripheral circulation.
● This pathway accounts for a minor component of normal destruction of
RBCs

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