Skin Cells

The skin cover the entire body and is our largest organ. It functions to protect the internal organs from mechanical, thermal, and chemical exposure as well as prevent evaporation of body liquids and of course also act as a barrier for pathogens. The outermost layer of the skin is called the epidermis. This layer varies in thickness depending on the location, but in general it is about 0.2 mm - 0.5 mm, or 200-500 microns thick. The epidermis can be subdivided into five (actually six) individual layers all made up mostly of skin cells, called keratinocytes. In fact 90-95% of the cells in the epidermis are keratinocytes.

Keratinocytes are roughly 30 microns, or 0.03 mm in size. But their size can vary quite a bit. Inside each cell we are able to see the nucleus roughly centered. We are also able to see tiny cellular granules and organelles as pale grainy dots. The cells in these photos are from a cheek swab, and the inside of our mouths are filled with millions of bacteria whether we like it or not. These bacteria can be seen on the cells as the small deeply blue coloured structures.

The deepest layer of the epidermis is called stratum basale. This layer contains stem cells able to divide and make more skin cells. This process happens so fast that the entire epidermis is renewed about once every month. But with that many new cells being made, we also need to lose some cells. As the basal layer produces more and more cells, the other cells gets pushed up toward the surface. On their journey through the different layers they change their appearance and content. They slowly get stiffer due to a high amount of the protein keratin and they also get flatter and flatter the closer to the surface they come. The final ‘real’ layer is called stratum corneum. Now the cells are completely stiffened, flattened and very loosely bound to one another. So when the skin is exposed to mechanical forces the skin cells are separated from the body in another “layer” called stratum disjunction. It is these cells we look at here.