|MadSci Network: Anatomy|
How many cells are in an adult human? Lots. More than anyone could count, and the bigger you are the more cells there would be. Growth is a process of cellular reproduction, so as you grow bigger you are made up of more cells. Following a similar logic, a larger person is larger because they have more cells, not because their cells are larger. In fact, cell types have a fairly uniform size across the entire human species.
The largest and smallest cells in the human body are the gametes, or the sex cells. The female sex cell, the oocyte, is about 35 microns in diameter, which puts it just on the edge of being visible if you have real good eyes. The male sex cell, spermatozoan, cell is only about 3 microns in diameter, and therefore is the smallest cell of the human body. Various other cell types have various other sizes within this range.
Admin note: Although no exact number can be given, the order of magnitude of the number of cells in a human body can be approximated to 10 14 or one hundred trillion cells.
Try the links in the MadSci Library for more information on Anatomy.