Hair Growth
As most people know, nothing in life is simple. The same can also be said for hair growth. Growing the hair that we all take for granted, is a complex process and something that very few people understand. Many people try to improve the health of their hair using hair growth products and treatments laced with hair growth vitamins etc. without knowing how, if or why these things will improve their hair. The other side of the coin is when people want to remove their hair but fail to understand the biology of hair growth and which treatments can do what.
Did you know that the hair on your body is essentially dead? There’s a lot to learn about hair growth but fear not, you will soon be a hair biology expert!
Anatomy of the Hair
If you take a look at the diagram above, you will see that the hair consists of a follicle beneath the skin layer. The hair that you see protruding from the follicle is the hair that you see on your body. The follicle is more complex than it appears and consists of several distinct layers which have individual functions in the hair growth process. At the base of the hair follicle you find what is know as the dermal papilla. Capillaries beneath the hair follicle, supply blood via the dermal papilla and to the bottom part of the hair strand which is known as the bulb.
The hair follicle is surrounded by an inner sheath and an outer sheath which run the length of the hair up to the sebaceous (oil) gland. You will also find the ‘erector pili’ which is the muscle that raises you hairs when you get ‘goose bumps’.
The shaft of hair itself is made up of three layers. Each layer consists of dead protein cells known as ‘keratin’. The ‘medulla’ is the name for the innermost layer. The second layer is the ‘cortex’ which provides the body of the shaft. This layer is mainly responsible for the color of your hair as it contains the pigmentation. The third layer is called the ‘cuticle’ and comprises of overlapping cells which provide the hairs sheen and luster.
What Happens When Hair Grows?
Hair growth can be defined into three main stages of growth. On average human scalp hair will grow between 0.3mm-0.4mm per day. Also remember that hair does not all grow at once. Whilst some hair follicles are starting a new hair, some are losing an old hair and some maybe half way through a hair. This is why some permanent hair removal methods require multiple treatments to catch each and every hair.
The three stages of growth are :-
The Catagen Growth Phase
The Catagen phase occurs just after the anagen stage (see later). Approximately 3 percent of your hair will be in this phase at any one time. This is a transitional phase that takes about two to three weeks. During this time, a ‘club hair’ is formed. This is when the hair follicle attaches to the hair itself and cuts the blood supply off from the growing hair. When this stage is complete, the Telogen stage is entered.
The Telogen Phase
This phase is better known as a ‘resting period’ for the hair. About 10% to 15% of your hair will be in this stage. This stage can last up to 100 days. During this phase, the club hair is completely formed. If you pull these hairs out, they have a hard white material at the root. You can shed as many as 100 Telogen hairs per day!
The Anagen Phase
The Anagen phase is the business end of the process. This is when the cells in the root of the hair are dividing rapidly and adding to the hair shaft. On the scalp, this phase can last a long time; approx. 2 to 6 years. At this point, a hitherto unknown signal causes the hair to enter the Catagen stage where the process begins all over again.
