Which cells of the skin are filled with a tough, fibrous protein and account for most of the epidermal cells of the skin?

Keratinocyte

Explanation:

Keratinocytes are primarily found in epidermis and its made up of 90% epidermal skin in man.

keratinocytes forms barrier that prevent us against environmental damage by heat, ultraviolet radiation, water loss from the skin, invasion of pathogenic bacteria, fungi, parasites, and viruses.

Keratinization is a form of the physical barrier formation where more keratinocytes is produced under terminal differentiation.