Question: how many cells are lost when you graze your skin???

Jeremy Green answered on 14 Jun 2011:

I would guess a few million, depending of course on the size of the graze (area and depth).

The more complicated answer is that the surface of your skin is not really cells at all but the dead husks of cells. Underneath that are cells that are very flat and spread out and that are designed to turn into those husks. This layer is maybe 5-10 cells thick. Then you get to a skin stem cell layer, or basal layer, which is a single layer of cells that constantly divide to produce the overlying cells. Below that are other types of skin cells, but this deep you’re seeing blood, so you’re through what most non-scientists recognise as skin. If each cell is a flat disc about 15 micrometers in diameter, then there are about 4,500 cells per square millimeter of skin in each layer. Say there are 10 cells thick, or 45,000 cells per square millimeter. A 1 cm X 1 cm graze is then 10 mm X 10 mm, i.e. 100 square mm, or 4,500,000 cells-worth if you remove them all.