Which epidermal layer forms the outer protective barrier composed of dead cells?

• A. Basal Membrane
• B. Stratum Corneum
• C. Thickness Variation
• D. Epidermis Blood Supply

Answer: (B)

The outer protective barrier of the epidermis is formed by the stratum corneum. This topmost layer consists of dead, flattened keratin-filled cells (corneocytes) that have lost their nuclei and desmosomes, creating a tough, waterproof shield. As skin cells mature in the deeper layers, they move upward, keratinize, and eventually become part of this outer layer, where they are shed. This dead-cell layer is essential for preventing water loss and protecting against environmental hazards. The basal membrane sits beneath the epidermis and serves as a boundary to the dermis, not as the outer protective barrier; thickness variation describes a characteristic rather than a layer, and epidermis blood supply is not a layer at all (the epidermis is avascular).