Cells of the Epidermis

The epidermis, the topmost layer of the skin, consists of four major cell types—keratinocytes, melanocytes, dendritic cells, and Merkel cells.

Keratinocytes form most of the epidermis. They produce a protein called keratin - a tough, fibrous protein that protects the skin and underlying tissue.

In response to the epidermal growth factors, the newly produced keratinocytes continuously push the older cells toward the skin surface.

By the time they reach the skin surface, keratinocytes die due to the lack of dermal blood supply and are replaced by new cells rendering a renewed epidermis every 25 to 45 days.

Melanocytes are spider-shaped cells found deep inside the epidermis. They produce melanin pigment, which is transferred to nearby keratinocytes through their processes. Melanin protects the nucleus of keratinocytes from the damaging effects of UV radiation.

Dendritic cells are star-shaped cells dispersed in the epidermis. They can ingest microorganisms and activate immune responses.

Merkel cells at the junction of the dermis and epidermis are linked to disc-like nerve endings forming the sensory receptor for touch.