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Guide to Structure of Hair, Hair Follicle and Hair Growth

Hair is made of strong elastic strands of protein called keratin and in chemical terms is composed of oxygen, iron, nitrogen, hydrogen, sulphur, carbon and phosphorus. The exact proportions of these chemical elements vary with sex, age, type and colour of hair.

The sources of hair are very small tiny pockets in our skin and scalp known as follicles. These follicles are not evenly spread on the scalp but are found together in groups of two to five each. Every follicle follows a life cycle of its own producing six inches of hair a year for as long as four years before it falls out then starts all over again after a short period.

The basal tip of the hair in the scalp is known as papilla which is a small out-growth of the skin shaped like a doorknob and lying at the tip of the follicle. The papilla contains the blood vessels to supply nourishment to the hair.

During the active period the new cell growth pushes the older part of the hair away from the papilla until the hair falls out. It is the pattern of cell growth at the papilla which determines whether hair grow straight wavy or curly.

The growth pattern usually becomes uneven during the adolescence when the hair growth is at its peak. It declines as we grow older. The cell growth pattern can change otherwise also due to illness, drugs, pregnancy, etc.

Though hair strands look as singular fibres, each hair is constructed in three different layers: the cuticle, the cortex and the medulla.

The cuticle is the outermost layer of the hair which provides protection to the inner cortex layer. It is made up of flattened, hard, horny cells. When the cuticle breaks and dislodges at the end of the hair, the result is split ends. Improper care and frequent use of harsh chemicals on hair damage the cuticle.

The cortex is the second layer. The qualitative properties of strength, elasticity, pliability, direction and growth pattern, width and the texture of hair depend on the composition of the cortex. The cortex is composed of fibres twisted together like a rope.

It is the cortex which gives the hair its colour. The presence of the four natural pigments black, brown, yellow and red are logged in the cortex in varying proportions, and the air spaces in the cortex determine the colour and shade of hair. The excess black and deep brown pigment is what gives oriental women the dark hair they possess.

Lastly, the medulla is the unimportant innermost layer which is composed of soft keratin. Medulla is often not present in some hair. Hair that lacks medulla is no worse than hair that has medulla.

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