Human hair in good condition is surprisingly strong - one hair can hold the weight of a chicken’s egg. It is a hard, fibrous substance. We have to be very careful how we treat it because, unlike skin, it is not alive and cannot repair itself. Therefore, we need to correctly maintain its balance of protein and moisture to keep it in good condition.
The percentage of protein in hair is between 83% and 87%. The percentage of moisture is about 3%. The balance is made up of sugar, salt and trace elements. If this essential balance is maintained, the hair will stay healthy and strong. It will be in good manageable condition, soft to the touch and with a natural shine.
The outer structure of the hair shaft consists of a collection of transparent layers of interlocking scales, which are collectively known as the cuticle. Most people have from 7 to 11 of these transparent layers all wrapped around the delicate inner part.
The delicate inner part of the hair shaft consists of a collection of spring like fibers that are coiled around each other and suspended in a glutinous material known as a fatty acid. This is where the moisture and hard and soft proteins are found.
The outer root sheath of the hair follicle encloses the inner root sheath and hair shaft.
The inner root sheath of the hair follicle is located between the outer root sheath and the hair shaft. It is made of three layers: Henle's layer, Huxley's layer, and the cuticle.
Cuticle: the outermost part of the hair shaft.
Cortex: located between the hair cuticle and medulla.
The hair matrix produces the actual hair shaft as well as the inner and outer root sheaths.
Papilla: large structure located at the base of the follicle, made up mainly of connective tissue and a capillary loop, cell division is either rare or non-existent.
References
http://www.tintsofnatureusa.com/about_haircolor.html
http://en.wikipedia.org/wiki/Matrix_(hair)
