Published on 04/03/2015 by admin
Filed under Hematology, Oncology and Palliative Medicine
Last modified 04/03/2015
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4 Megakaryocyte maturation
Platelets arise from the megakaryocyte. Megakaryocytes are among the largest cells in the body and mature by a unique process called endomitosis. In endomitosis, the nucleus is duplicated but there is no cell division, resulting in a polyploid cell. Megakaryocyte nuclei may have from 2 to 32 lobes and, in unusual cases, may have up to 64 lobes. Megakaryocytes develop copious cytoplasm, which differentiates into platelets. Platelets have several types of granules that can be visualized by electron microscopy. The granules are highly specialized. Refer to a hematology textbook for further discussion.
FIGURE 4–1 Megakaryocyte sequence—megakaryoblast MK-I.
FIGURE 4–2A Megakaryoblast, MK-I—bone marrow (×1000).
FIGURE 4–2B Megakaryoblast, schematic.
10-24 μm
Round
2-6
Homogeneous, loosely organized
Absent by Wright stain
3:1
20% of megakaryocyte precursors in bone marrow
0%
Note:
The megakaryoblast appears similar to the myeloblast and pronormoblast, and identification by morphology alone is not advisable.
FIGURE 4–3 Megakaryocyte sequence—promegakaryocyte (MK-II).
Clinical Hematology Atlas
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