Megakaryocytes simply mean cells with a large nucleus and they are found in the bone marrow. Normally, there is 1 megakaryocyte for every 10,000 cells of the bone marrow. These megakaryocytes break into smaller pieces and give rise to platelets.
A megakaryoblast is a large, single-nucleated cell in the bone marrow that is the precursor to megakaryocytes, which are the cells that produce platelets