Keratin is defined as "a hard, fibrous, sulphur-containing protein with an alpha-helix structure, found in the epidermis of vertebrates, mainly in the outermost layers of skin. Keratin can have several forms: in scales, feathers, hooves, horns, claws and nails it is hard, while wool and hair are made up of a soft and flexible form."
When the natural protection of the foreskin for the glans penis is unavailable, the human body is noted for its ability to apply a layer of keratin to the glans penis as substitute protection. This is a late complication of circumcision and results in a partial loss of sensation in the glans penis. This process is called keratinization.
- Wikipedia article: Keratin. Retrieved 14 January 2023.
Keratin, The Free Dictionary by Farley. Retrieved 14 January 2023.