Epidermis

Function

The epidermis is a self-renewing fortress of keratinocytes — five layers from the mitotic basal layer to the flattened corneocytes shed daily as household dust. Its Langerhans cells patrol as immune sentries; its melanocytes donate melanin caps that shield basal DNA from ultraviolet light.

Avascular and fed by diffusion from the dermis, it rebuilds its barrier within 48 hours of a superficial wound — the speed that makes split-skin grafting possible.

Blood supply

Diffusion from dermal capillaries only.

Nerve supply

Free nerve endings signal itch and pain; specialized Merkel cells give light touch.

Clinical relevance

Psoriasis

Immune-driven keratinocyte turnover accelerates 10-fold — thick silver scales over red plaques on elbows and knees.

Squamous and basal cell carcinoma

UV-induced skin cancers — BCC the commonest cancer of all, SCC arising in actinic damage.

Related conditions

• Psoriasis