What is keratinization in hair biology?

• A. Process where cells change their shape, dry out, and form keratin protein.
• B. The process of hair growth from follicles.
• C. The enzymatic breakdown of hair proteins.
• D. The shedding of cuticle scales from the hair shaft.

Answer: (A)

Keratinization is the maturation of hair-forming cells into keratinized, dead cells that compose the hair shaft. As these cells move from the follicle toward the surface, they change shape, dry out, and accumulate keratin protein, forming the hard, resilient fiber of hair. This is what gives hair its strength and structure. It’s not about hair growth from follicles, enzymatic breakdown, or shedding of cuticle scales—the keratinization process specifically describes how living cells harden into the keratin that makes up the visible hair.