Main Page | See live article | Alphabetical index A blood cell is any cell of any type normally found in blood. In mammals, these fall into three general categories: red blood cells, whose main purpose is the transport of oxygen white blood cells, which act as immune cells and fight infection Platelets, which are actually fragments of the large bone marrow cells known as megakaryocytes and are important in blood clotting This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.