148
UNIT 2
Basic Tissues
Figure 8-11A.
Orthochromatophilic erythroblasts, bone
marrow smear.
Wright stain,
3
710; inset
3
1,569
The
orthochromatophilic erythroblast
, also called a
normoblast
, is a very small cell, close to the size of an
erythrocyte. The nucleus is small and so condensed that
it looks like a dark dot because of the extreme condensa-
tion of the chromatin. The cytoplasm appears pinker than
that of the
polychromatophilic erythroblast
. Hemoglobin
production and accumulation are almost complete, with
few ribosomes left in the cytoplasm. At this stage, the cell
is unable to divide. Orthochromatophilic erythroblasts
become reticulocytes (Fig. 8-11B) after losing their nuclei.
D. Cui
OE
Orthochromatophilic
erythroblast
Proerythroblast
Proerythroblast
Proerythroblast
PoE
PoE
Orthochromatophilic
erythroblast
A
CLINICAL CORRELATION
Figure 8-11C.
Reticulocytosis, Peripheral Blood
Smear.
New methylene blue stain,
3
1,020
Reticulocytosis
is a condition characterized by an
increased number of reticulocytes.
Reticulocytes
are
premature red blood cells. The normal percentage of
reticulocytes is 0.5% to 1.5%.
Hemolytic anemia
usu-
ally increases erythropoietin production, which in turn
causes the bone marrow to produce more red blood
cells, resulting in a reticulocyte percentage of above
4% to 5%. An increased number of reticulocytes in
peripheral blood is an important indication of
hemo-
lysis
(
red
blood
cell
rupture
) or
bleeding
. It can also
be the consequence of treating the anemia of chronic
kidney disease with erythropoietin. This illustration
shows the increased number of reticulocytes with new
methylene blue stain after hemolytic anemia.
Erythrocyte
Reticulocytes
C
D. Cui
Capillaries
Mature
erythrocyte
(inside of capillary)
Reticulocyte
Orthochromatophilic
erythroblast
(normoblast)
B
Figure 8-11B.
Reticulocytes: the f
nal step o± erythro-
cyte ±ormation.
Orthochromatophilic erythroblasts
have small and highly
condensed nuclei. In the next stage, the nucleus is extruded
and phagocytosed by
macrophages
. Although the cells
loose their nuclei, they retain some
polyribosomes
in their
cytoplasm. When stained supravitally with cresyl blue or
new methylene blue, the ribosomes aggregate into a blue
reticular network; therefore, the cells are called
reticulo-
cytes
. Reticular cells appear the same as mature erythro-
cytes with Wright stain (Fig. 8-11C). Reticulocytes enter
the blood circulation through the bone marrow sinusoidal
capillaries and become mature erythrocytes in one or two
days. Mature erythrocytes have neither nuclei nor organ-
elles and appear as a biconcave disk.
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