Which sequence lists the epidermal layers from superficial to deep?

• A. Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale
• B. Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum
• C. Stratum lucidum, Stratum corneum, Stratum basale, Stratum granulosum, Stratum spinosum
• D. Stratum corneum, Stratum granulosum, Stratum lucidum, Stratum spinosum, Stratum basale

Answer: (A)

The layers of the epidermis are organized from the surface down in a specific order that reflects how keratinocytes mature and move toward the protective outside. The outermost layer, stratum corneum, is made of dead, flattened keratinocytes that form the tough barrier you see on the skin’s surface. In thick skin, a thin, clear layer called stratum lucidum sits just beneath the corneum and adds extra protection. Deeper still is the stratum granulosum, where keratinocytes accumulate keratin and begin to flatten and keratinize as they prepare to become part of the protective surface. Beneath that lies the stratum spinosum, a living, metabolically active layer where cells are connected by desmosomes, lending structural strength. At the bottom is the stratum basale, a single layer of proliferating cells that continually replaces those shed from above and anchors to the underlying dermis.

So the superficial-to-deep sequence is: corneum, lucidum (when present), granulosum, spinosum, basale. This arrangement also aligns with how epidermal renewal works: new cells are born in the basale, move upward through the spinosum and granulosum, and finally become the dead keratinized cells in the corneum.