Hair Structure

Hair Structure

Hair structure, is not something that most people with think about, if a product or styling method works, then it doesn’t really matter about the actual nuts and bolts of Hair.

That being said, there are a lot of reasons why the Hair structure and growth cycle of hair may interest you.

Through this post I am going to try and not just boringly relay facts of what hair is and then show diagrams, I shall try and incorporate this into applicable knowledge. things that you may take into account when growing or cutting your hair or even colouring and bleaching. to do this though we are going to have to start at the beginning, so…

What Is Hair

Hair is Simply protein, a protein called Keratin. Keratin is a strong fibrous protein that makes up not only our hair but also our skin. It can be for pretty frequently in the animal kingdom from shells of turtles to beaks of birds. I find this truly amazing that the formation of fibrous proteins, the same as our hair, can make something as strong as a birds beak. Nature is a fascinating place.

The hair shaft is actually in three layers, this at first doesn’t seem that important to know, but it is as later in this post shows. The three layers from most inner to outer

The Medulla


The Medulla is the inner most part of the hair if the hair would be cut as a cross section, although it is not really known what the function of the medulla is, it probably has something to do with insulation of heat or protection. That is just my theory though, nothing has been proved on this. The Medulla is not always present in the hair, on naturally light hair or hair that is very fine, it is not present.

The Cortex

The Cortex is the main body of the Hair shaft, it is the second layer of the hair. This is where all the melanin ( a broad therm used for a group of pigments) this is responsible for the colour of the hair, the Cortex is the where the strength and elasticity of the hair is. This layer is important to know as this is where your chemical treatments take place, colouring, perming and bleaching, all effect this part of the hair in different ways. For example it is the cortex that bleaching breaks down the molecules of the hair, making it lighter in colour. the bigger the molecules the darker the hair. Permeant and quasi hair colours also effect this layer. The colour molecules enter and therefore alter the colour of the hair shaft.

The Cuticle

The Cuticle is the outer most layer of the hair it is formed by over lapping scales that lay over the cortex, protecting it. The cuticle is the first part of the hair to get damaged by heat, chemicals and environmental influences. When this gets damaged you will be able to notice, the hair will loose its shine and feel rougher and dryer.

Interestingly with this layer of hair, and why it’s important to know is that when these “scales” lay flat they reflect the light very well. So as you dry with a brush keep the air flow facing down the hair shaft. Straightening also flattens the layers of the cortex creating this shiny look to the hair.

Thats a basic look at the layers and structure of the hair, it may not seem important but now after reading about it, you can see how things like chemical process and styling effect the look, feel and health of the Hair. I will bring up these layers more in my step by steps on this site, especially the cuticle which, styling wise at least is the most important part. If that layer is healthy then it is protecting the Cortex and therefore the whole hair is healthy.

Now we’ve looked at what it is, lets look at how it grows. This next chapter is about the growth cycle of hair as a standard. I want to write a dedicated post about hair loss and the forms of it, so this doesn’t take any effect or change brought on by stress diet or medication. This is more of an overview.

The Human Hair growth cycle

The human hair growth cycle is pretty standard across the board, Regardless of where the hair is situated on your body.

The growth cycle are broken down into three main stages they Are called anagen (growth phase), catagen (transitional phase), and telogen (resting phase) phases. Each strand of hair on the human body is at its own phase keeping a steady amount of hair at any one time. Also meaning that you are naturally loosing hair all of the time. I brought this up briefly in another post on shampooing myths. Where I said there was nothing to worry about, when you shampoo and see hair in hands.

Hair grows at a relatively steady rate. Obviously this can vary a lot on external factors, such as stress diet or medication. But The rate of hair growth is about 1.25 centimetres or 0.5 inches per month, or about 15 centimetres or 6 inches per year. However as we will see when we look at phase 3 in more detail. This isn’t a continuous on going growth.

Anagen phase

The anagen phase is known as the growth phase. It begins in the papilla (A small nipple-like protrude in the skin) and can last from two to six years. The longer the hair stays in the anagen phase, the longer it will grow so if you have hair that grows naturally long, you could guess that you have a cycle closer around the 5-6 year mark. If, on the other hand you struggle to get your hair to grow past shoulder length, this is your answer. Like I said this is an over view so I know 2-6 years is a fairly big margin for error. The span at which the hair remains in this stage of growth is determined by genetics (sorry) During this phase, the cells in the papilla divide to produce new hair fibres, and the follicle of the hair shaft goes deeper into the dermal layer of the skin increasing the blood supply. About 85% of the hairs on your head are in the this phase at any given time

Catagen phase

The catagen phase, also known as the transitional phase, allows the follicle to, rest . During this time, which lasts about two weeks, the Hair strand is cut off from its blood supply.This stage affects about 1% of the hair on your head at a time

Interestingly even though the hair isn’t growing anymore. Because the follicle pushes the hair up, it gives it the appearance of looking longer.

Telogen phase

During the Telogen or resting phase This last about 1-4 months, like I have said before, even though each person goes through the same cycle, The duration of that cycle is totally genetic and individual. About 10% of hairs on your head are in the telogen phase at any one time. After this the hair detach and shed at a rate of around 50 to 100 hairs per day.

To repeat, this is totally down to genetics so if you have a short cycle, your hair probably won’t grow to the length of a persons who had a long cycle. This is by no means a bad thing and having a short or long cycle is completely irrelevant when it comes to having nice, healthy hair.

Many things can effect this cycle stress, diet, medication, pregnancy To name but a few. One thing I would say, is if you are feeling worried about the amount of hair you are loosing it might be worth looking at your diet. Obviously this is not medical advice and if you are seeing problems please visit a doctor or trichologist. But stress and diet do effect the hair. So one piece of advice to end is, Don’t stress about hair loss, stress effects the body in such an extreme and negative way that it is better to be avoided at all costs. I realise trying not to stress about something is one of the hardest things to do. But we have so many things to worry and stress about, don’t let your hair become one more log on the pile. Maybe try and be a bit kinder to yourself, maybe meditate for 5/10 mins a day. Everyone can create that time in their day and it will have a big effect on you in more ways than just your hair.

Thanks for reading.


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