Page 224 - Atlas of Histology with Functional Correlations

occupies most of the cell. The chromatin is dispersed uniformly, and two or

more nuclei may be present. Azurophilic granules are absent from the cytoplasm
in all cells of the erythrocytic series. The proerythroblasts (3) divide to form the
smaller basophilic erythroblasts (8, 16).

Basophilic erythroblasts (8, 16) are characterized by a rim of basophilic
cytoplasm and a decreased cell and nuclear size. The nuclear chromatin is coarse

and exhibits the characteristic “checkerboard” pattern. Nucleoli are either
inconspicuous or absent. Basophilic erythroblasts (8, 16) give rise to the
polychromatophilic erythroblasts (12), which are similar in size to basophilic
erythroblasts (8, 16). The cytoplasm of the polychromatophilic erythroblast (12)

becomes progressively less basophilic and more acidophilic as a result of
increased hemoglobin accumulation. The nuclei of polychromatophilic
erythroblasts (12) are smaller and exhibit a coarse checkerboard pattern.

When the polychromatophilic cells (12) acquire a more eosinophilic (pink)
cytoplasm as a result of increased hemoglobin accumulation, their size decreases

and they become orthochromatophilic erythroblasts (late normoblasts) (1).
These cells are capable of mitosis (2). Initially, the nucleus of
orthochromatophilic erythroblasts (1) exhibits a concentrated checkerboard

chromatin pattern. Eventually, the nucleus decreases in size, becomes pyknotic,
and is extruded from the cytoplasm, forming a biconcave-shaped cell with a
bluish pink cytoplasm called a reticulocyte or young erythrocyte. With special
supravital staining, a delicate reticulum is seen in the reticulocyte cytoplasm
because of the remaining polyribosomes (see Fig. 6.14). After polyribosomes are

lost from the cytoplasm, the cells become mature erythrocytes (9) and enter the
systemic circulation via the numerous blood channels. Erythrocytes (9) are small
cells with a homogeneous eosinophilic, or pink, cytoplasm.

Also visible in the bone marrow smear are different types of myelocytes and

metamyelocytes of the granulocytic cell line. Myelocytes exhibit an eccentric
nucleus with condensed chromatin and a less basophilic cytoplasm with few
azurophilic granules. Different types of myelocytes exhibit varying number of
granules. More mature myelocytes, such as neutrophilic myelocytes (14), an

eosinophilic myelocyte (15), and a rare basophilic myelocyte (11), show an
abundance of specific granules in their slightly acidophilic cytoplasm. The
myelocyte is the last cell of the granulocytic line capable of mitosis, after which
they mature into metamyelocytes.

The shape of the nucleus in the neutrophilic line changes from oval to one
with indentation, as seen in neutrophilic metamyelocytes (4). Before complete

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