CHAPTER 8
Blood and Hemopoiesis
147
Erythropoiesis
Figure 8-10A.
Proerythroblasts, bone marrow smear.
Wright stain,
3
710; inset
3
1,569
The
proerythroblast
is a relatively large cell with a
large, round nucleus containing two to three nucleoli.
The cytoplasm appears
basophilic
(blue) because of the
presence of a large number of ribosomes. At this stage,
the cell is beginning to accumulate the necessary com-
ponents for the production of
hemoglobin
. Proeryth-
roblasts are precursor cells, which develop from two
functionally identiF
able progenitor cells:
burst-forming
unit–erythroid
(
BFU-E
)
cells
, which take about a week
to mature to become
colony-forming unit–erythroid
(
CFU-E
)
cells
and another week to become proerythro-
blasts. Proerythroblasts undergo mitosis to produce two
daughter cells that will develop the features of
basophilic
erythroblasts
.
D. Cui
Proerythroblast
Proerythroblast
Proerythroblast
PoE
Proerythroblast
Proerythroblast
Proerythroblast
Nucleoli
Proerythroblast
OE
A
B
D. Cui
Basophilic
erythroblast
Basophilic
erythroblast
Basophilic
erythroblast
Basophilic
erythroblast
Basophilic
erythroblast
PoE
OE
BE
BE
Figure 8-10B.
Basophilic erythroblasts, bone mar-
row smear.
Wright stain,
3
710; inset
3
1,569
The
basophilic erythroblast
is smaller than the pro-
erythroblast, and its cytoplasm is deep blue because
of a high content of tightly packed
ribosomes
. Com-
pared to proerythroblasts, basophilic erythroblasts have
smaller nuclei with a coarser texture because most of
the chromatin is in the heterochromatin form. At this
stage, nuclei are less active than in proerythroblasts, and
their nucleoli disappear. These cells undergo mitosis and
divide into daughter cells, which mature to become
poly-
chromatophilic erythroblasts
. (OE, orthochromatohilic
erythroblast; PoE, polychromatophilic erythroblast; BE,
basophilic erythroblast.)
C
D. Cui
Basophilic
erythroblast
Polychromatophilic
erythroblast
Polychromatophilic
erythroblast
Polychromatophilic
erythroblast
Polychromatophilic
erythroblasts
Orthochromatophilic
erythroblast
Figure 8-10C.
Polychromatophilic erythroblasts, bone
marrow smear.
Wright stain,
3
710; inset
3
1,569
The
polychromatophilic erythroblast
is smaller than
its parent cell (
basophilic erythroblast
). The nucleus is
smaller and it has no nucleoli. The condensed nucleus is
densely stained, and it displays a patchy pattern because
of condensation of chromatin. The cytoplasm of the cell
is usually grayish in overall color because, at this stage,
signiF
cant amounts of
hemoglobin
have been produced
and accumulated in the cytoplasm, so that the staining
of the cytoplasm refl ects the presence of both ribosomes
(basophilic) and hemoglobin (eosinophilic). Therefore,
the cytoplasm is mottled with mixed patches of blue and
pink (
polychromatophilic
means “attracting multiple
colors”). Polychromatophilic erythroblasts undergo
mitosis and divide into daughter cells that develop into
orthochromatophilic erythroblasts
.
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