Friday, January 26, 2007

Is your hair dead or alive?

Many people believe they can do anything to their hair because its dead anyway.
Is this true? Well yes and no.
The hair outside of your scalp is psychologically dead, it has no blood, nerves or muscles. When you cut it there is no pain, and it does not bleed.
However, for a dead fiber, it is quite remarkable. Healthy hair can be stretched up to 30% of its length, can absorb it own weight in water and can increase its diameter by 20%.
We can change its colour, its shape, curl it, wash it, brush it, set it, pull it and rub it to an amazing degree.
And yet despite all of this, our hair can remain resilient and tough.
Hair is composed of Keratin, a fibrous protein. And is built from cells similar to our skin.
The hair shaft consists of three layers: the outer cuticle, composing of overlapping layers, like fish layers; The Cortex, comprising the hair’s main bulk and colour; and the Medulla, a thin core of transparent cells and air spaces.
Each one of us is born with a specific number or hairs, which cannot be changed.
Hair grows from a single follicle. At the base of these follicles is the Papilla, the bud of the hair where most growth takes place. Each follicle has its own blood, nerve and muscle supply.
The blood capillaries surrounding the follicle carry the nourishment needed for cell production and growth. [More on this later]
Hair grows on average about half an inch a month. Faster in summer than in winter. Its normal growth phase lasts between three to five years. After a short resting phase the hair will normally fall away.
The follicle then lies dormant for three months then the cycle repeats itself.
Each follicle has its own independent cycle.
The average head carries 120.000 hairs. Blondes tend to have more, redheads less.