Hair Structure

Hair is a protein filament that grows from follicles deep within the skin. The average number of hair follicles on an adult human being is estimated at 5million, out of which 1 million are on the head. 100'000 of these alone cover the scalp. The hair follicle can be recognised as a separate entity within the skin, with formation and maintenance based on interaction between dermal and epidermal components. Below the surface of the skin is the hair root which is enclosed within the hair follicle. At the base of the follicle is the dermal papilla which is fed nutrients through the bloodstream and so produces new hair. The dermal papilla is a structure that is very important to hair growth as it contains receptors for androgenic hormones and male hormones. The role of androgen is to regulate the growth of new hairs. In scalp hair however, androgen may cause the hair follicles to become progressively smaller, resulting in the hairs becoming much thinner and finer in individuals who are genetically predisposed to this type of hair loss.

The hair itself consists of three layers: an outer cuticle, the middle cortex and the central medulla. If the hair is coloured it is due to the presence of pigments - melanin is found in black or brown hair and pheomelanin is found in red or yellow hair. If there are no pigments present then the hair appears to be white. Grey hair, or Canities as it is also known, is an illusion created by the combination of white and coloured pigments in single strands of hair. Individual "grey" hairs do not exist. As mentioned previously, hair grows from a follicle. The walls of this follicle form the outer root sheath of the hair, and the lower part of the follicle broadens to form the hair bulb containing the germinal matrix - the key source of hair growth. Dermal tissue projects into the follicle base to form the dermal papilla which has a network of capillary blood vessels supplying oxygen, energy and amino acids that are crucial for the growth of healthy new hairs.