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Erythropoiesis
Erythropoiesis is the highly regulated multistep process, the end
product of which is the erythrocytes or red blood cells.
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Modified,Page36,Willams-Hematology
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FACTORS REGULATINGERYTHROPOIESIS
SINGLE MOST IMPORTANT REGULATOR:
TISSUE OXYGENATION
ERYTHROPOIETIN
BURST PROMOTING ACTIVITY
IRON
VITAMINS:
Vitamin B12
Folic Acid
MISCELLANEOUS
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STEM CELLS
These cells have extensive proliferative capacity
and also the:
Ability to give rise to new stem cells (Self Renewal)
Ability to differentiate into any blood cells lines(Pluripotency)
They grow and develop in the bone marrow.
The bone marrow & spleen form a supporting
system, called the
hemopoietic microenvironment
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Pluripotent Stem cells: Has a diameter of 1823 .
Giving rise to: both Myeloid and Lymphoid series ofcells
Capable of extensive self-renewal. Myeloid Stem cells: Generate myeloid cells:
Erythrocytes
Granulocytes: PMNs, Eosinophils & Basophils.
Thrombocytes.
Lymphoid Stem cells: Giving rise only to: Lymphocytes: T type mainly.
STEM CELLS: Types
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PROGENITOR CELLS
Committed stem cells lose their capacity for self-
renewal.
They become irreversibly committed.
These cells are termed as Progenitor cells
They are regulated by certain hormones or
substances so that they can:
Proliferate Undergo Maturation.
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Myeloid
stem cell
BFU-E
CFU-E
Pronormoblast
Erythrocytes
Erythropoiesis
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ERYTHROPOIESIS: SEQUENTIAL CHANGES
I II III IV VVIPRONORMOBLAST
Basophilic
normoblast
Polychromatic
normoblast
RETICULOCYTE
MATURERBC
MITOCHONDRIABASOPHILIAHEMOGLOBIN
Orthochromatic
normoblast
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ERYTHROID PROGENITOR CELLS
BFU-E: Burst Forming UnitErythrocyte:
Give rise each to thousands of nucleated erythroid
precursor cells, in vitro.
Undergo some changes to become the Colony FormingUnits-Erythrocyte (CFU-E)
Regulator: Burst Promoting Activity (BPA)
These are more closely related to the multipotent stem cell.Contain moderately basophilic cytoplasm with occasional pseudopods,.
very fine nuclear chromatin and large nucleoli.
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CFU-E: Colony Forming Unit- Erythrocyte:Well differentiated erythroid progenitor cell.
Present only in the Red Bone Marrow.
Can form upto 64 nucleated erythroid precursor cells.
Regulator: Erythropoietin.
ERYTHROID PROGENITOR CELLS
Cell morphology
Fine nuclear chromatin.
Well defined large nucleolus.
High nuclear cytoplasmic ratio, a perinuclear clear zone
Basophilic cytoplasm with pseudopods.
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Normoblastic Precursors
PROERYTHROBLAST:
Large cell: 1520 microns in diameter.
Cytoplasm is deep violet-blue staining
Has no Hemoglobin.
Large nucleus 12 microns ,occupies 3/4th of the
cell volume.
Nucleus has fine stippled reticulum & manynucleoli.
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Basophilic erythroblast:
Smaller in size.
Shows active Mitosis.
No nucleoli in the nucleus.
Fine chromatin network with few condensation
nodes found.
Hemoglobin begins to form.
Cytoplasm still Basophilic.
Normoblastic Precursors
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Polichromatic Erythroblast:
Has a diameter of 1014 microns.
Shows active Mitosis.
Increased Hemoglobin content in the cytoplasm
Cytoplasm is Polychromatophilic.
Normoblastic Precursors
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Orthochromatic Erythroblast:
Diameter is 710 microns.
Nucleus shrinks with condensed chromatin.
Nucleus undergoes the pyknotic degeneration
and exnucleation .
Cytoplasm has a Eosinophilic appearance.
Normoblastic Precursors
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RETICULOCYTE:
The penultimate stage cell.
Has a fine network of reticulum like a as
clumps of dots The presence of reticulum leads to the term
reticulocytes
In the Neonates, Count is 26/Cu.mm.
Reticulocytosis is the first change seen inpatients treated with Vit B12
Normoblastic Precursors
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MATUREERYTHROCYTE:
Biconcave disc.
No nucleus. About One-third filled
with Hemoglobin.
Normoblastic Precursors
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Life Cycle of Red Blood Cells
Figure 17.7
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