Final answer:
A. Keratin is the primary structural protein in the epidermis, nails, and skin, making them tough and water-resistant. It is produced by keratinocytes, which are abundant in the epidermis.
Step-by-step explanation:
The primary structural protein of the epidermis, nails, and skin is keratin. This tough, fibrous protein provides hardness and water-resistant properties. Keratinocytes, the cells that produce keratin, are the most predominant type of cells found in the epidermis. Nails, composed of keratin, include parts such as the nail body, nail cuticle, and nail root. The nail bed is actually the portion of skin over which the nail plate resides, and the nail grows from the nail root, not from the distal end.
- Keratin is the primary structural protein for the epidermis, nails, and skin.
- Keratinocytes in the epidermis produce keratin, giving these structures their toughness.
- Nails are primarily composed of keratin and exhibit growth from their roots.