Final answer:
The stratum corneum forms a protective barrier layer thanks to a combination of keratin-filled dead keratinocytes and glycolipids, making it tough and waterproof.
Step-by-step explanation:
The stratum corneum is the outermost layer of the epidermis, which acts as a protective barrier between the body and the environment. It is composed mainly of dead keratinocytes that have undergone keratinization, a process where they become filled with keratin. This layer is tough and waterproof because of the high concentration of keratin and glycolipids. Together, they provide a barrier that not only prevents the penetration of microbes but also minimizes water loss from the underlying tissues. The stratum corneum is continually renewed as dead cells shed and are replaced by new ones from lower layers, notably the stratum granulosum.
Additionally, the skin has a mechanical protection role; it protects against abrasions, thanks to the durability of the keratin-filled cells in the stratum corneum. Sweat glands also play a role in protection by secreting dermicidin, an antibiotic substance, to prevent the over-colonization of microbes on the skin surface.