Function of the Skin

Epidermis

The epidermis's uppermost section of the skin comprises five distinct layers or strata of cells that collectively form stratified epithelial tissue.

A basement membrane connects the dermis and the epidermis, through which the tiny papillae penetrate. The epidermis provides the outermost section of the skin, from which individual hairs protrude and onto which sebum and sweat are released. The surface skin cells, hairs, sweat, and sebum form a protective barrier that is resilient and strong enough to withstand superficial attack. Over approximately one month, the epidermis cells travel up from the basement membrane to the surface, changing as they enter each layer.

Most skin cells are known as keratinocytes. Keratinocytes are cells capable of producing the protein keratin, responsible for forming the skin, hair, and nails surface. The epidermis layers can be divided into sections or zones, including a germinating (growing) and a keratinization (hardening) zone. The keratinocytes in the germinating zone are healthy, living, reproducing cells. However, they change when they reach the keratinization zone.

These changes result in the hardened and dead cells continuously being shed from the skin’s surface in a process known as desquamation. The thickness of the layers that form the skin varies across the body. Skin is thickest on the soles of the feet and thinnest over the eyelids.