Structure of the Hair

Hair is made up of dead cells.
On our heads, we have hundreds of thousands of follicles, pore-like structures within the scalp that produce hair. Each follicle produces many hairs throughout our lifetime.
Live hair cells are generated inside the follicle by the papilla. As the new cells grow, the older cells die and are forced along the follicle towards the scalp. The dead cells are compressed to form a protein called keratin. The hair shaft that we see is the keratin emerging from the scalp. Finger-nails are made of keratin, too.Each hair consists of keratin, small amounts of water and a binding agent, which holds the keratin and water together.

The Structure of Hair
Hair is made up of several layers:
The outer, protective coating of the hair is formed from overlapping scales and can be several layers thick. These scales are what makes the hair flexible. The outer coating is translucent, which allows the colour of the hair (from the cortex) to be seen. You can make the scales 'open up' to allow chemicals and other substances to penetrate the hair.
The main bulk of the hair consists of long fibres, twisted together to form a rope. This is the cortex. At the centre of the finest threads of the cortex are three spiral, spring-like chains that are bonded together. It is these chains that give hair its ability to stretch and allow us to direct the hair into different styles.

The chains (polypeptide chains) are held together by three types of bond:
di-sulphide or sulphur
The di-sulphide bonds are the ones you need to break if you want to change the shape of the hair permanently but you need break only 25 to 30 percent of the bonds, ie less than one third.

The cortex determines the colour of the hair. There are two pigments:
melanin, which gives us brown and black
pheomelanin, which gives us yellow and red
Medulla-This is the centre of the hair shaft. It does not play a part in hairdressing....