Keratin is the main constituent of the stratum corneum of tetrapods and especially the amniotic
Keratin is a protein found in the skin of several species of vertebrates (reptiles, mammals and birds) and plays a protective function by physical and chemical stress. also prevents dehydration caused by the loss of water from the skin, which is crucial for those animals that live independent of the presence of water.
It’s a filamentous protein rich in sulfur, contained in amino acid residues of cysteine; It is very stable and durable. It is a quaternary structure, composed of more tertiary structures placed one after the other. It is produced by keratinocytes, and is immersed in their cytosol as intermediate filaments.