Hair Explained - The Anatomy and Physiology of Hair
Hair is mainly composed of a protein called keratin (about 88%). Keratin starts out as a soft substance arising from the follicle and keratinizes (hardens) as it rises up and out into the hair shaft. Keratin is insoluble, very tough, and highly elastic. The Follicle is an indentation that pushes down into the deep layers of the skin, and is where keratin develops. The Sebaceous gland is the individual hairís well of natural oil. Too much or two little production of oil from this gland can cause symptoms of oiliness or dryness in the hair and scalp.
Cuticle The thinnest, outer layer. Composed of transparent, overlapping, protective, scale-like cells pointing away from the scalp. Protects inner structure of the hair and is effected by chemical, physical, and thermal damage.
Cortex The middle layer, comprising 75- 80% of the hairís protein structure. Held together by a bond of positive and negative charges. Gives hair its strength and elasticity. Contains pigments which give hair its colour.
Medulla The central axis of hair, containing a column of soft keratinised cells interspersed with air pockets, helping to give hair its elasticity.
In general, hair exists as one of these three shapes. As it grows, the hairshaft assumes the shape, size and direction of the follicle.