Which epidermal layer marks the start of keratinization and contains granules?

Which epidermal layer marks the start of keratinization and contains granules?

• A. Stratum Lucidum
• B. Stratum Granulosum
• C. Stratum Corneum
• D. Stratum Germinativum

Answer: (B)

Keratinization begins as epidermal cells enter the Stratum Granulosum. In this layer, cells flatten and accumulate keratin along with keratohyalin granules that help organize and condense the keratin filaments. As they move through this layer, the cells start to degenerate their nuclei and organelles, signaling the transition toward a keratinized, waterproof layer. The presence of these granules, plus the release of lipids from lamellar bodies that contribute to the skin barrier, are hallmarks of the onset of keratinization. The outer Stratum Corneum is fully keratinized and dead, while the Stratum Germinativum is where cell division occurs, and the Stratum Lucidum (when present) appears only in thick skin. This combination makes Stratum Granulosum the correct layer.

Keratinization begins as epidermal cells enter the Stratum Granulosum. In this layer, cells flatten and accumulate keratin along with keratohyalin granules that help organize and condense the keratin filaments. As they move through this layer, the cells start to degenerate their nuclei and organelles, signaling the transition toward a keratinized, waterproof layer. The presence of these granules, plus the release of lipids from lamellar bodies that contribute to the skin barrier, are hallmarks of the onset of keratinization. The outer Stratum Corneum is fully keratinized and dead, while the Stratum Germinativum is where cell division occurs, and the Stratum Lucidum (when present) appears only in thick skin. This combination makes Stratum Granulosum the correct layer.