Page 229 - Atlas of Histology with Functional Correlations

SECTION 2 • Bone Marrow

Located in medullary cavities between bony trabeculae

Red bone marrow is the principal site of hematopoiesis
Consists of cords and islands of hematopoietic stem cells that replace lost
cells
A branching capillary network surrounds hematopoietic stem cells
The site of macrophage breakdown of worn-out erythrocytes and storage of

iron

DEVELOPING BLOOD CELLS

Development of Erythrocytes

Precursor proerythroblast shows a rim of basophilic cytoplasm and a large

nucleus
Early basophilic erythroblasts are smaller and exhibit large nuclei and
basophilic cytoplasm
Polychromatophilic erythroblasts exhibit more condensed nuclei and more

eosinophilic cytoplasm
Increased hemoglobin accumulation, eosinophilic cytoplasm, and decreased
size produce orthochromatophilic erythroblasts (late normoblasts)
Most recognizable erythrocytic lines are normoblasts with early stages

exhibiting mitosis
Mature normoblasts lose the ability to divide, extrude their highly condensed
pyknotic nuclei, and become eosinophilic erythrocytes
Erythrocytes do not exhibit cytoplasmic granules as they enter systemic

circulation

Development of Granulocytes

Myeloblast, first recognizable granulocytic cell line, gives rise to
promyelocyte
Early granulocytes exhibit numerous azurophilic granules in the cytoplasm

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