What is "stratum corneum"

n. (context anatomy English) The outer layer of the epidermis, composed of dead cells that continually flake away

n. the outermost layer of the epidermis consisting of dead cells that slough off [syn: corneum, horny layer]

The stratum corneum ( Latin for 'horny layer') is the outermost layer of the epidermis, consisting of dead cells ( corneocytes). This layer is composed of 15-20 layers of flattened cells with no nuclei and cell organelles. Their cytoplasm shows birefringent filamentous scleroprotein keratin. The stratum corneum is composed of three lipid components: ceramides, cholesterol, and fatty acids.

The purpose of the stratum corneum is to form a barrier to protect underlying tissue from infection, dehydration, chemicals and mechanical stress. Desquamation, the process of cell shedding from the surface of the stratum corneum, balances proliferating keratinocytes that form in the stratum basale. These cells migrate through the epidermis towards the surface in a journey that takes approximately fourteen days.