epidermaal

Epidermaal is an adjective used in anatomy and dermatology to describe anything related to the epidermis, the outermost layer of the skin in vertebrates. In humans and other mammals, the epidermis forms a stratified squamous epithelium that serves as a protective barrier, helps prevent water loss, and contributes to protection from UV radiation through pigment-containing cells.

Structure and cells

The epidermis consists of several sublayers: stratum basale, stratum spinosum, stratum granulosum, and, in thick skin, stratum lucidum, with the outermost layer being the stratum corneum. Most cells are keratinocytes, which originate in the basal layer and migrate outward as they accumulate keratin and eventually die, forming the cornified surface. Other cell types include melanocytes (pigment production), Langerhans cells (immune function), and Merkel cells (sensory touch).

Function and renewal

The epidermis is avascular and relies on diffusion of nutrients from the underlying dermis. Basal cells continuously proliferate to replace shed cells, yielding a turnover of roughly 28 days in a healthy adult. The stratum corneum provides a water-resistant barrier, while melanin helps modulate UV exposure.

Clinical relevance

Epidermal disorders include psoriasis, which involves hyperproliferation of keratinocytes, and eczema or dermatitis, which affect barrier function. Bullous diseases such as epidermolysis bullosa involve defects at the epidermal-dermal junction. Epidermaal concepts are also central to skin grafting and wound healing, where restoration of the epidermal layer is essential.

Etymology

The term derives from Greek epi-, meaning upon, and derma, meaning skin. In common usage, epidermaal forms part of discussions on epidermal structure and function.