The epidermis continuously renews itself, with cells migrating from the basal layer at the junction with the dermis to the external barrier layer of dead cells where they are shed.1

Keratinocytes account for about 80 per cent of epidermal cells. These harden with the protein keratin as they travel through the epidermal sublayers, eventually maturing into corneocytes or horny cells forming the stratum corneum. Other notable epidermal cell types include pigment-synthesising melanocytes and Langerhans cells involved in T cell immune responses.

Hair grows from the dermis through the epidermis, emerging from the hair follicle. Sebaceous glands, which secrete the lipid-based sebum, sit in the dermis, and apocrine sweat glands - involved in scent release - sit in the subcutaneous fat layer, mainly in the axillae (armpits) and perineum. Both discharge into the hair follicle close to the dermis-epidermis junction.

Eccrine sweat glands (for temperature regulation) also sit in the epidermis but secrete directly onto the skin surface. Cells in the eccrine gland ducts undergo keratinisation.

Apoeccrine glands develop from eccrine-like precursors during puberty and secrete directly onto the skin surface in axillae. They can secrete up to 10 times more sweat than eccrine glands, an issue in axillary hyperhidrosis.

A disruption in the function of any of these skin structures can result in blemishes, spots, or pustules.