In order to define Keratinin a proper way it is necessary to describe the organ skin and especially one of its parts, the epidermis.
The epidermisis the superficial layer of the skin, it stands above dermis and hypodermis and is composed by five layers: basal layer, spinous layer, granular layer, clear layer and cornfield layer.
The epidermis is characterized by a continuous cellular change.
The cells originate in the basal layer as a result of a mitosis duplication and move upward modifying their shape and functions.
The cells that originate from the basal layer are called KERATINOCYTES.
Keratin and Tricopigmentation
Once keratinocytes reach the granular layer they insert in their cytoplasm keratoialin granules that will turn the cells themselves into keratin filaments.
Keratin confers hardness, compactness and protection to the skin.
Keratin is a grey protein.
Keratin is present especially in thick skins like for example those of the scalp, skins characterized by hyperkeratosis, senescent skins etc., that are indeed characterized by a grey color.
Keratin is present not only in the skin but also in all its cutaneous annexes such as nails and hair.
It has exactly the same function.
Also in this case keratin is a grey protein at the matrix of nails and hairs and it changes when in contact with the external environment.
In the hair bulb keratin looks grey and soft when the hair grows and then when the hair gets longer other proteins such as melanin confer a different color, ranging from blond to dark brown according to the amount of melanin.
This is why shaved hair and body hair always look grey. Our eye can see the grey color of keratin and not the color given by melanin yet.