1.1 POJA-L607. Ultrastructure of a megakaryocyte

1.1  POJA-L607

Title: Megakaryocyte
 
Description: Scheme electron microscopy.

The megakaryocyte is derived from a promegakaryocyte which originates from splenic stem cells (CFU-S , colony forming units-spleen). The megakaryocyte is a giant polyploid cell (35-160 mm) and contains a large multilobate nucleus (1).

The perinuclear area shows Golgi areas (2), centrioles (3) and mitochondria (4). The granular population can be divided into homogeneous electron-dense d granules (5) and homogeneous electron-grey ones (6) (lysosomes) and electron-grey ones with a dark centre (7) (a granulum) (↓, arrows).  Especially the intermediate zone shows many granules, glycogen (8), localized in cytoplasmic areas (ca. 2-4 mm) that are subdivided by an interconnected tubular system (so-called demarcation membrane system (DMS, 9). These demarcation channels traverse the marginal zone enriched by cytoskeletal filaments (10) and are in continuity with the irregular cell surface. The dense tubular system is hardly visible.

Background: 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.
 
Keywords/Mesh: blood, bone marrow, megakaryocyte, platelet. demarcation membrane system, histology, electron microscopy, POJA collection

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