What layer of the epidermis is responsible for cell division?

The stratum basale, also known as the stratum germinativum, is the deepest layer of the epidermis and is primarily responsible for cell division. This layer is composed of a single row of columnar or cuboidal cells that are constantly undergoing mitosis. As these cells divide, they push older cells upward through the layers of the epidermis towards the surface. This continual process of cell division is essential for the renewal of the skin and helps in repairing any damage that may occur at the surface.

In contrast, the stratum corneum consists of dead, flattened keratinized cells that have already completed their lifecycle, with no further division occurring there. The stratum granulosum serves as a transitional layer where cells begin to flatten and lose their nuclei, which is a sign that they are moving away from the division phase. The stratum spinosum contains larger cells that may still participate in some metabolic activities, but it is not the primary layer for active cell division. Thus, the stratum basale is crucial for maintaining the integrity and regeneration of the skin through its role in cell division.