Which layer of the epidermis is considered the oldest?

The oldest layer of the epidermis is the stratum corneum. This layer consists of dead skin cells that have lost their nuclei and other organelles, making them flattened and filled primarily with keratin, a protective protein. As the outermost layer, the stratum corneum plays a crucial role in the barrier function of the skin, protecting underlying layers from environmental damage, pathogens, and water loss.

Cells in this layer are continuously shed and replaced by cells that move up from the deeper layers of the epidermis, such as the stratum granulosum and stratum spinosum. Because the cells in the stratum corneum are at the end of their lifecycle and are constantly being renewed, they are considered the oldest within the epidermis. This characteristic contributes to the overall health and resilience of the skin, as well as its ability to perform essential functions.