Blood platelets are disc-shaped, non-nucleated cell fragments that range in diameter from 2 to 4 µm. In actuality, platelets are not cells. They come from fragments of the cytoplasm of megakaryocytes that live in the red bone marrow.
WBCs are the largest blood cells. Leucocytes make up only over 1% of the blood volume, Leucocytes and erythrocytes differ in several ways:
1. Each leucocyte has a nucleus, mitochondria, and other organelles, proving that they are actual cells.
2. There is no Hb in them.
3. Erythrocytes are not movable, although leucocytes are.
4. Leucocytes can exit veins and penetrate the surrounding tissue, while erythrocytes typically do not leave the vascular system.
5. The lifespan of the majority of leucocytes is relatively short.
