What layer of the skin acts as a barrier against bacteria and moisture?

The epidermis is the outermost layer of the skin and serves as the primary barrier against environmental threats, including bacteria and moisture. It is composed of several strata of cells, primarily keratinocytes, which produce keratin, a protein that adds strength and waterproofing qualities to the skin. This barrier function is crucial in preventing the entry of pathogens and minimizing moisture loss from the underlying tissues.

In contrast, the dermis, which lies beneath the epidermis, contains connective tissues, blood vessels, hair follicles, and sensory receptors, playing a vital role in supporting the epidermis but not primarily serving as a barrier. The subcutaneous tissue and hypodermis, while important for insulation and cushioning, do not contribute directly to the protective barrier function that the epidermis provides. Hence, the epidermis is recognized as the key layer responsible for safeguarding the body from external threats.