Keratinocyte

Keratinocyte — the most abundant cell type in the epidermis, responsible for producing keratin, a tough structural protein that helps form the skin's protective barrier. These cells move upward from the base of the epidermis as they mature, eventually flattening and shedding from the surface.

Key points

• Keratinocytes make up roughly 90 percent of the cells in the outer epidermis.
• They originate in the basal layer and gradually migrate upward while filling with keratin in a process called keratinization.
• As they reach the surface they form the stratum corneum, the outermost layer that limits water loss and blocks external irritants.
• The full cycle of a keratinocyte moving from the basal layer to shedding takes roughly four weeks in healthy adult skin.

Frequently asked

What is the main job of a keratinocyte?

Keratinocytes produce keratin and build the outer skin barrier, helping retain moisture and protect against microbes, pollutants, and physical damage.

How are keratinocytes related to skin cell turnover?

Skin cell turnover describes keratinocytes maturing from the basal layer to the surface and shedding, a cycle that can slow with age and influence skin texture.

Related topics

• What Is a Humectant?
• What Is the Skin Barrier?

This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.