Which layers contribute to the barrier function of the skin?

• A. The dermis and hypodermis
• B. Subcutaneous tissue only
• C. The corneum and intercellular matrix
• D. Stratum basale only

Answer: (C)

Barrier function is provided by the outermost epidermal layer, the stratum corneum, along with the intercellular lipid matrix that sits between the corneocytes. This brick-and-mortar arrangement—dead keratin-filled cells (corneocytes) held together by a lipid-rich matrix of ceramides, cholesterol, and fatty acids—forms a waterproof barrier that minimizes water loss and blocks entry of chemicals and microbes. The deeper layers, like the dermis and hypodermis, mainly contribute to structure, support, and nourishment rather than forming the primary barrier. Subcutaneous tissue is fatty tissue and isn’t the barrier either. The stratum basale is the living layer that regenerates epidermal cells, not the barrier.