Know about hair structure:
The hairs on our heads is mainly made of a though protein called keratin and is made of two parts:
The root or hair bulb – the living part of the hair, is embedded in a hair follicle (in other words, hair bulbs forms the base of the hair follicle, where living cells divide and grow to build the hair shaft). Blood vessels nourish the cells in the hair bulb and deliver hormones that modify hair growth.
The Shaft – is the visible part of the hair, however biologically its dead, it is made up of dead keratin-filled cells. The shaft itself is structured in three different layers:
The medulla: This is the soft, central part of the hair shaft, composed of agglomerated cells with no nucleus. Normally, thick hair contains large amounts of medulla, while fine hair has almost none.
The cortex: This is the thickest layer of your hair. Envelops the medulla and is composed of two types of keratin fibres – horizontal and vertical, which makes the hair supple and strong. It also contains the melanin pigments that gives hair its colour. In other words, cortex provides strength, colour and texture of the hair.
The cuticle: the outermost layer of the hair and made up of keratin scales that overlap one another like tiles in a roof. Hairs are covered in an oily layer of sebum produced by the sebaceous gland embedded in each hair follicle. This substance is essential to their good health. It protects them, nourishes them and keeps them soft and shiny. In other words, the cuticle is the tough, protective outer layer of your hair.
Hair colour comes from melanin, a natural pigment produced by cells called melanocytes, located in the root. There are two different types of melanin:
First type: Eumelanin (brown to red colour), is responsible for brown, dark and black hair.
Second type: Phaeomelanin (red to yellow) colours blond and red hair.
The colour is more and less intense, depending on the amount of melanin present in the hair. Each person’s hair colour is determined by their DNA, but external factors (sun, salt and plus) can contribute to lightening it. With age, melanocytes decrease and become scarce and this is when the hairs start to get grey or white, which are almost devoid of melanin.
Hair Life Cycle:
Throughout our life, our hair grows, falls out and grows again. Each hair follicle is capable to producing approximately 15 successive hairs before its activity stops and it dies. Hair growth is not continuous and it takes place in three successive stages:
The Anagen Stage - which last for 3 to 7 years, during which the hair grows approximately 0.3mm per day (or 1cm per month). New Keratinocytes are produces in the hair bulb and push the oldest ones out, thus lengthening the hair.
The Catagen Stage – which last 3 to 4 weeks, during which the hair bulb keratinocytes degenerate then die. The bulb then slowly migrates towards the surface of the scalp. In other words, hair growth slows and the hair follicle shrinks.
The Telogen Stage – which lasts 3 to 4 months, the hair is shed naturally. This is followed by a rest period during which nothing happens, before a new cycle begins. In spite of these different stages our hairs go through, our hair density remains visibly constant (except in cases of alopecia). This is because at any given moment, approximately 90% of our hair is in he anagen stage: the few dozen hairs we lose each day therefore go unnoticed.