What is Hair?

About 95% of hair is made of a tough protein called keratin. Keratin is synthesized by keratinocytes and is insoluble in water, enabling impermeability and protection for the hair. Hair plays a significant role in personal identity but also has a purpose and is beneficial overall for your body.

Hair structure can be divided into three distinct parts:

  • Medulla: innermost layer of the hair shaft, composed of an amorphous, soft, oily substance.

  • Cuticle: thin protective outer layer that contains the nourishing portion essential to hair growth.

  • Cortex: main component of the hair, containing long keratin chains that add elasticity, suppleness, and resistance to the hair. The cells of the cortex are joined together by an intercellular cement rich in lipids and proteins.

A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. In the hair bulb, living cells divide and grow to build the hair shaft.

Humans have the same amount of hair as apes! The number of hairs on humans is not that much less than on apes, there being about 60 hairs per square centimeter on our naked skin. But human hairs are small and have less pigment than hairs on apes. The reduced density and size of human hair makes heat loss through sweating and evaporation more efficient.