Final answer:
Keratin is the fibrous protein in our skin that provides protection against abrasion, and it is also found in hair and nails. Melanin, sebum, and elastin have different roles in skin health and structure.
Step-by-step explanation:
The fibrous protein in our skin that protects it from abrasion is keratin. This protein is not only present in the skin but is also a key structural component of hair and nails. Keratin is essential for the protection of epithelial cells from damage or stress and forms a protective layer on the outside of the skin. In contrast, melanin provides pigment and protection against ultraviolet (UV) light, sebum is an oily substance that lubricates the skin and hair, and elastin fibers enhance the flexibility of the dermis. Nails are predominantly composed of keratin, and within the epidermis, keratinocytes produce keratin. Moreover, melanin can be found in these keratinocytes. The constant regeneration of the epidermis allows the skin to remain intact even when superficial layers are removed, as new cells are always being produced.