Red Marrow (Myeloid tissue)
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RED MARROW (MYELOID TISSUE)
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It is composed of stroma of reticular cells and fibres with free cells located in the meshwork. The stroma also shows varying number of fat cells. Majority of free cells in bone marrow are the developmental stages of the granulocytes and a few lymphocytes, monocytes and plasma cells. Sinusoids are numerous and form anastomosing networks.
Haemocytoblasts:
Erythroblasts:
These are the precursors of erythrocytes and undergo a series of divisions and transformation before the erythrocytes is formed. The important stages in erythrocyte formation are;
Myelocytes:
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These differentiate from myeloblasts. These constitute 12 percent of the marrow cells. These cells show an increase in the granules and increase in the density of chromatin of the nuleus. The earliest myelocytes are known as Promyelocytes. They are large cells with rounded or oval nucleus and basophilic cytoplasm. The cytoplasm contains a few granules of one of the specific types (neutrophilic or acidophilic) but because of the few granules promyelocytes are not classified into three groups. The promyelocytes proliferate and differentiate into myelocytes proper. The cells become smaller in size show an increase in the number of granules, decrease in the basophilia of cytoplasm and increase in the density of the chromatin of the nucleus.
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Neutrophilic, esoinophilic and basophilic myelocytes are distinguished. The myelocytes after a number of generations, differentiate into metamyelocytes. They have an indented or kidney shaped nucleus and the cytoplasm showing numerous specific granules of each type. The metamyelocytes differentiate into mature leucocytes, which enter the blood stream.
Megakaryocyte:
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Last modified: Friday, 20 August 2010, 12:27 PM