Which skin layer is primarily made up of living cells that divide and replenish the outer layer?

The correct answer is the Basal Layer, also known as the stratum basale. This layer is the deepest part of the epidermis and contains actively dividing cells, called keratinocytes, that continually produce new cells. As these cells divide, older cells are pushed up toward the surface of the skin, eventually leading to the formation of the outermost layer, the stratum corneum.

The Basal Layer plays a crucial role in maintaining the health of the skin by constantly replenishing the outer layers, which are eventually shed due to normal wear and tear. This process is vital for skin regeneration and helps in healing and protecting the skin.

Other skin layers have different roles. The stratum corneum consists of dead cells that are no longer living and primarily serve as a protective barrier. The dermis is the layer beneath the epidermis that contains connective tissue, blood vessels, and nerves, but it does not divide and replenish the outer layer itself. The stratum Malpighii, which includes both the stratum basale and the stratum spinosum, refers to the deeper layers responsible for cellular proliferation, but the basal layer specifically emphasizes the actively dividing cells.