Skin cell. Coloured scanning electron micrograph (SEM) of a keratinocyte skin cell (centre) with a large central nucleus (orange). Keratinocytes are found in the epidermis layer of the skin. They are rich in proteins called cytokeratins. The cytokeratin filaments extend into the junctions between cells, which are known as desmosomes. Desmosomes help the cells to withstand mechanical stress.