Which epidermal layer contains a single layer of mitotically active columnar cells?

The stratum basale is the deepest layer of the epidermis and is comprised of a single layer of mitotically active columnar or cuboidal cells. These cells are primarily responsible for the production of new keratinocytes, which will eventually move up through the layers of the epidermis, undergoing differentiation and keratinization. The presence of mitotically active cells is critical for the continuous renewal of the skin, as they ensure the replacement of cells that are shed from the surface of the skin.

This layer also contains melanocytes, which produce the pigment melanin, contributing to skin color and protection from UV radiation. Additionally, it includes Merkel cells, which are involved in touch sensation. The stratum basale is essential for maintaining the integrity and health of the epidermis, ensuring that the outer layers of skin are populated with fresh, healthy cells.

The other layers mentioned do not have the same characteristics; the stratum corneum, for instance, is composed of dead, keratinized cells and does not have mitotically active cells. The stratum granulosum contains keratinocytes that are undergoing the process of keratinization, while the stratum spinosum has keratinocytes that are in an earlier stage of