TRICHOLOGY: THE STUDY OF HAIR
Individual strands of hair grow out of follicles on the scalp, which are formed in fetal life. Hair consists of two parts: THE ROOT which is actually under the surface of the skin, in the follicle, and THE SHAFT (or strand), which is the part of the hair that you can see. The actual strands of hair are not alive, but rather and outgrowth of keratinized cells that grow out of the living hair bulb, inside the follicle. The texture of the hair (straight, wavy or curly) is determined by the shape of the follicle.
The strand of hair consists of two main parts: THE CUTICLE which is the outer covering of the strand of hair and THE CORTEX which is the centre of the hair strand. The cuticle is a layer of transparent scales which protects the cortex. Over time, the cuticle may become damaged through chemical processing, brushing or combing, and environmental factors, which can lead to split ends, tangles, matting of hair, and other problems as the cortex becomes exposed. The cortex gives the hair it's pigment(colour) and also elasticity.
Hair growth occurs in three stages:
1.ANAGEN: This is the stage where hair is actually growing. At any given time, about 90% of the hair on a person's scalp is in the anagen stage. This stage last from 2-6 years.
2.CATAGEN: This is a transitional stage where hair stops growing, and hair remains in this stage only a few weeks
3.TELOGEN: This is the stage where the hair strand falls out. This stage lasts 3-4 months, and at any given time about 10% of the strands on a person's scalp are in this stage.
After the hair falls out, the cycle starts over. Each individual hair follicle can produce a hair about 20 times throughout a human life time. The scalp sheds roughly 40-100 hairs a day, and though that may seem like a lot, it really isn't when you consider a head of hair consists of anywhere between 90,000 to 150,000 individual strands of hair.
Your hair's natural colour is determined by the MELANIN which is a type of pigment. There are two types of melanin: EUMELANIN which is brown/black and PHEOMELANIN which is red. All natural hair colour is determined by the amount and distribution of eumelanin and/or pheomelanin. A person with albino hair lacks all melanin, and there for has no pigmentation in their hair. When melanin in the cortex is reduced, the result is grey hair. The strands of hair are actually white, not grey. It is the mix of white hairs with pigmented hairs that gives the overall appearance of grey. Hairs will grow white from the scalp, as opposed to pigmented strands turning white.