stratum corneum

noun

stratum cor·​ne·​um -ˈkȯr-nē-əm 

: the outermost layer of the epidermis that consists of keratin-rich corneocytes connected by desmosomes and embedded in a matrix of lipids (such as ceramides and cholesterol) arranged in bilayers and that regulates skin permeability, maintains hydration, provides structural integrity, and acts as a protective barrier (as against UV radiation, pathogens, and toxins)

Note: In humans, the stratum corneum is typically 12 to 20 cell layers thick but may be over 50 layers thick in the soles of the feet and less than 9 layers thick on the eyelids. The outer layers are continually shed with one corneocyte cell layer typically sloughed off every day as desmosomes are enzymatically broken down.

The stratum corneum barrier relies predominantly on the extracellular matrix, where lamellar bilayers block the outflow of water into the environment … .

—Peter M. Elias et al.

A primary function of the stratum corneum is to protect the underlying tissue from environmental injury.

—Discover

Examples of stratum corneum in a Sentence

Recent Examples on the Web

The pH increases as the stratum corneum gets thinner, becoming pale, dull, uneven, and dry. —Mark Gurarie, Verywell Health, 30 Oct. 2024

Retinoids thin out the stratum corneum, which is the outermost layer of the skin that’s composed of dead skin cells. —Jamie Friedlander Serrano, TIME, 17 Oct. 2024

These exfoliants remove dead skin cells from the outermost layer of the skin called the stratum corneum through the use of a grainy substance like a scrub or chemicals like glycolic acid. —Jamie Wilson, Glamour, 8 Aug. 2024

Dehydration is when there is a lack of water in the stratum corneum or outer layer of the skin. —Alicia Lansom, refinery29.com, 10 Jan. 2024

Word History

Etymology

New Latin, literally, horny layer

First Known Use

1857, in the meaning defined above

Medical Definition

stratum corneum

noun

plural strata cornea

: the outer more or less horny part of the epidermis consisting chiefly of layers of dead flattened nonnucleated cells filled with keratin