Megakaryocyte (bone marrow, rabbit)

Electron microscopy. A survey of a megakaryocyte demonstrates very well the differences in diameter between this giant polyploid cell (1) and the other young white blood cells (2-5). In the intermediate zone the (dark) granules (of the future platelets) are close associated with the electron-light interconnected tubular system (so-called demarcation membrane system or open canalicular system: OCS) (→). These demarcation channels are continuous with the irregular cell surface. The production of platelets occurs after a long thin cytoplasmic cell extension protrudes through an endothelial fenestra resulting in the release of platelet ribbons or individual platelets. (2) myeloblast; (3) eosinophilic granulocyte; (4) young neutrophilic granulocytes; (5) adipocyte; (6) erythrocyte.