| Description |
Scheme electron microscopy. These disc-shaped anucleate cells (2-4 m) are derived from cytoplasmic fragments of the megakaryocyte. They contain few mitochondria, a canalicular system, a smooth tubular system, marginal localized microtubules, glycogen and different types of granula. A circumferential band of these microtubules (1, arrows) is responsible for the characteristic shape of the platelet. The canalicular system presents as interconnecting vacuoles that open at the surface (*). Electron-grey delta granules (5) contain plasma-absorbed serotonin, calcium ions, ADP and ATP etc., while the alpha-granula (2) variable in size and shape, contain among others platelet-derived growth factor, factor VIII (von Willebrand), thrombospondin, fibronectin, fibrinogen. (3) mitochondria, (4) glycogen, (6) dense tubular system. |
