Loss Books Links Men's Health Hair grows in three stages, consequently you never have a full head of hair as some hair is in the resting stage of growth. The hair is composed of a protein called keratin. The hair itself is arranged in three layers, an outer cuticle, middle cortex and central medulla. If these pigments are lacking the hair is white. Canites is the term given to grey hair, it is an illusion created by the mixture of white and coloured hairs.
Hair grows from a follicle.
The walls of the follicle form the outer root sheath of the hair. The lower part of the follicle widens out to form the hair bulb that contains the germinal matrix, the source of hair growth. Dermal tissue projects into the follicle base to form the dermal papilla, and this has a network of capillary blood vessels to supply oxygen, energy and the amino acids needed for growth. Melanocytes are present in the upper part of the papilla, producing pigment granules that are distributed throughout the cortex. In the follicle the hair is surrounded by an inner root sheath that has three layers.