Which describes Keratinization?

Which describes Keratinization?

• A. New cells form in the stratum basale and move upward, but do not die.
• B. Keratinization is the process of melanin production.
• C. The stratum corneum is composed of living, nucleated cells.
• D. New cells form in the stratum basale and move upward, becoming flat, hard, and eventually die to form a dead layer at the skin's surface.

Answer: (D)

Keratinization is the process by which epidermal cells mature as they move toward the surface, becoming flat, hard, and ultimately dead to form the outer protective layer. New cells form in the stratum basale and migrate upward through the epidermis; as they progress, they keratinize—accumulating keratin and losing their nuclei and organelles—so that by the time they reach the surface, they are dead, keratin-filled cells that make up the stratum corneum. This explains why the outermost skin layer is composed of dead cells and why keratinization is essential for a strong, waterproof barrier. The other statements don’t fit: keratinization is not melanin production, and the outermost layer is not living, nucleated cells.

Keratinization is the process by which epidermal cells mature as they move toward the surface, becoming flat, hard, and ultimately dead to form the outer protective layer. New cells form in the stratum basale and migrate upward through the epidermis; as they progress, they keratinize—accumulating keratin and losing their nuclei and organelles—so that by the time they reach the surface, they are dead, keratin-filled cells that make up the stratum corneum. This explains why the outermost skin layer is composed of dead cells and why keratinization is essential for a strong, waterproof barrier. The other statements don’t fit: keratinization is not melanin production, and the outermost layer is not living, nucleated cells.