The hair is made up of keratin, a protein structure. The hair consists of three layers. They are:
 

• The central core, known as medulla, is made up of spongy tissues, which may contain some colour pigment.  

• The middle layer, known as the cortex, consists of long thin cells, which give the hair its elasticity and colour.  

• The outer layer, known as cuticle, consists of hundreds of tiny, overlapping scales.
   

• Hair is formed in minute pockets in the skin, called follicles.  

• An up growth at the base of the follicle, called the papilla, actually produces hair, while a special group of cells turns amino acids into keratin. 

• The rate of production of these protein 'building blocks' determines hair growth. 

• The average growth rate is about 1.2 cm per month, growing fastest on women between the ages 15 to 30 years.  

• The sebaceous gland, which secretes the oil that gives healthy hair, its natural shine is located half way along the hair follicle. 

• The follicles, which contain the hair roots, are fed by blood carrying nutrients. 

• Good circulation is thus of utmost importance to healthy hair.  

• It is the supply of nutrients, which determines the health of the hair as it emerges from the scalp and continues to grow. 

• Once hair leaves the follicle, it is in fact technically 'dead' but it grows because of continued tissue formation within the follicle.
   

•  A disturbance in the production of sebum by these glands can result in over dry or greasy hair. Thus, if the glands become blocked or are under active, the hair will be greasy. 

• The natural color of hair and its shape straight or curly are determined by hereditary factors. In case of curly hair, the actual shape of the hair follicle forces the emerging hair to develop waves.  

• The number of individual hair ranges from 90,000 to 14,000, depending on the natural hair colour.  

• The number of hair roots or the texture of the hair cannot be changed except the natural changes, which occur with age.  

• The life span of a hair varies from several months to several years, depending on the scalp and hair conditions. The average life of hair is five years.  

• After that, the follicle from which the hair is growing begins to shrink and the hair remains static until it drops out or is brushed out and is replaced a few months later by a new hair. 

• Although a large number of hair may come out in a single day, the density of the hair will still remain the same.

• The trouble starts when a new hair does not form in the follicle due to inadequate blood supply, or glandular or hormonal imbalance.