corneous

Corneous is an adjective used in anatomy, histology, and zoology to denote horn-like or keratin-rich material. It derives from Latin corneus, meaning horned, and is related to, but distinct from, terms such as cornea. In human anatomy, the term often refers to the corneous or cornified epidermal layer, i.e., the stratum corneum, which consists of flat, dead keratinocytes (corneocytes) embedded in a lipid-rich matrix. This corneous layer forms the skin’s outer barrier, protecting against environmental exposure and limiting water loss. The term is also applied to other keratinized structures such as nails and hair.

In zoology and veterinary anatomy, corneous describes tissues and structures composed primarily of keratin. Examples include beaks, claws, hooves, and the outer keratinized scales of some reptiles. In horns, the visible outer sheath is corneous keratin that covers a bony core; the proportion and texture of the corneous layer vary among species. The distinction between corneous and osseous or cartilaginous components is commonly noted in this context.

In medicine and pathology, alterations of the corneous layer reflect changes in keratinization. Conditions such as hyperkeratosis or parakeratosis describe abnormal thickening or maturation of the corneous layer and are characteristic features of various dermatologic diseases.