It rests on top of the dermis from which it is separated by the dermal-epidermal junction. Consisting of a stratified structure, its average thickness is 1mm.
4 types of cells are found here:
The epidermis is made up of 4 cellular sublayers:
Cell renewal or the keratinisation process
The epidermis is in a constant state of renewal. In the basal layer, the keratinocytes are produced and then divide into two identical cells. One will remain in place and continue to divide, while the other will gradually migrate up to the horned layer – the external and visible part of the epidermis.
This is the differentiation process.
At the end of this migration, the keratinocytes unlodge the corneoctyes (= keratinocyte that has lost its nucleus), which are then shed as squames. This shedding phenomenon known as desquamation is the final stage in the life of an epidermal cell. It takes between 21 and 28 days.
This is cellular renewal.