What is the outermost layer of the skin called?

The outermost layer of the skin is known as the stratum corneum. This layer plays a crucial role in protecting the underlying tissues from environmental damage, preventing water loss, and serving as a barrier to pathogens and chemicals. It consists primarily of dead keratinized cells that are continuously shed and replaced, which helps to maintain skin integrity and overall homeostasis.

Each of the other layers mentioned carries out important functions in the skin's structure and health, but they are situated beneath the stratum corneum. For example, the stratum lucidum is found only in thicker skin areas, like the palms and soles, and consists of a few layers of flattened, dead keratinocytes. The stratum granulosum is characterized by cells that begin to lose their nuclei and cytoplasm is filled with granules containing keratin and lipids, contributing to the skin's waterproof barrier. The stratum spinosum contains living keratinocytes and is involved in the immune response of the skin.

In summary, the stratum corneum is the outermost and protective layer, making it essential for maintaining the skin's overall health and function.