Even though we give so much attention to the hair on our heads did you know that only about 1.6- 3% of our hair is located on our scalp1? Hair is a protein fibre (mainly made of keratin) produced in the follicles (the little pits) found over most of the skin (except for parts of the hands and feet). The thinner hair all over our bodies is called vellus hair, whereas the thicker, coarser type (including the hair on our heads) is named terminal hair. Hair growth originates in the hair bulb and the part that we see is referred to as the hair shaft.
The scaly outer part of the hair is called the cuticle and is the bodyguard of the inner cortex. The cuticle’s overlapping layers determines how well your hair holds on to moisture (which will spoken about a little later :D) and once damaged the harm to the strand can never be reversed! It’s goodbye to the other layers, an appointment with the scissors will be needed to regain healthy hair.
The second layer is the boss layer: the cortex. If you want shine and vibrant colour, look after your cortex (actually I’m lying, look after the cuticle and the cortex will mostly be taken care of). The cortex is where approximately 90% of your hair is found and it’s where we get our hair colour and structure from2. Hair colour depends on how much melanin is produced by the melanocytes (the cells which make melanin, and therefore the colour of our skin and hair). The lighter the hair colour, the less melanin in the cortex (except for redheads who have a different kind of melanin). The cortex is where relaxers, curly perms and colouring treatments attack to change the nature of the hair.
The most inner layer, the medulla, can perform a disappearing act. In fine or blond hair the medulla vanishes, so why have a medulla I hear you ask? Well the only known function of the medulla is its ability to reflect light causing our hair colour to change in various environments3. (I tried to make the function of the medulla sound cool but compared to the other layers the medulla is pretty lame, sorry guys :P).
I bet you’re thinking, ‘Geez, so much info for such a little bit of protein!’ My friends, it’s only the tip of the iceberg! Next time I’ll be talking about hair growth and will be trying to convince you that all hair can grow to any length! (Believe me, please believe me!)
1. Krause, K; Foitzik, K (2006). Biology of the Hair Follicle: The Basics. Seminars in Cutaneous Medicine and Surgery, Volume 25, Issue 1.