Definition of Platelet

1. Atrial Fibrillation Slideshow Pictures
2. Bad Bugs and Their Bites Slideshow
3. Understanding Ulcerative Colitis Slideshow

Platelet: An irregular, disc-shaped element in the blood that assists in blood clotting. During normal blood clotting, the platelets clump together (aggregate). Although platelets are often classed as blood cells, they are actually fragments of large bone marrow cells called megakaryocytes.