Which layer of the epidermis is responsible for mitosis and replacement of damaged skin cells?

The correct answer is the stratum basale, which is the deepest layer of the epidermis. This layer is primarily responsible for the mitosis and regeneration of skin cells. It contains basal cells that actively divide to produce new keratinocytes, which then migrate upwards through the layers of the epidermis. As these new cells move towards the surface, they undergo differentiation and keratinization, which enhances the skin’s protective barrier.

The stratum corneum, being the outermost layer, consists of dead, flattened keratinized cells that provide a barrier to environmental factors but does not contribute to cell division. The stratum granulosum contains keratinocytes that are undergoing a process of keratinization, but it is not where mitosis occurs. The stratum spinosum is above the stratum basale and contains several layers of keratinocytes that give the skin strength and flexibility; while it plays a role in some cellular processes, mitosis primarily takes place in the stratum basale. Thus, the stratum basale is crucial for the continuous renewal and repair of the skin.