Which of the following describes the outer layer of dead epithelial cells that limits absorption?

• A. Dermis
• B. Hypodermis
• C. Stratum Corneum
• D. Epidermis

Answer: (C)

The outer barrier of the skin is the stratum corneum. This is the topmost part of the epidermis made up of dead keratin-filled cells (corneocytes) that have shed their nuclei and are embedded in a lipid-rich matrix. This structure creates a tight, waterproof barrier that greatly limits the diffusion of substances into and through the skin, as well as reducing water loss. While the broader epidermis includes living layers beneath, the stratum corneum is the specific layer described as dead epithelial cells forming the main barrier at the surface. Dermis and hypodermis are deeper connective tissue layers, not the outer dead epithelial layer.