Basic Hair Anatomy

Welcome back friends! Ever heard someone say their hair is “dead”? Yep, me too! And this isn’t actually accurate..

I wanted to share with you all about the basics of hair- what is it, how it grows, and the structure of each individual hair. So if this is something you’re interested in (I know, science-y stuff isn’t for everyone but ya girl’s a hair nerd).

Hair is made up of a protein called keratin, which I’m sure you’ve heard of. It has three layers, the cuticle which is the outer layer and has a scale-like structure, the cortex which is where the color molecules and all the bonds live, and the very inner section is called the medulla which you may or may not have depending on how fine or coarse your hair is. The medulla doesn’t really have a known purpose, but it is basically the marrow of hair. If you have fine hair you may not have one and that’s okay- it doesn't play a part in chemical hair services.

The cortex is the middle layer and this is where the structure of the hair comes from. Your natural hair pigments (melanin) are in this layer, as well as the building blocks to your hair. Speaking of building blocks, these are the bonds that hold your hair in a specific shape and give your hair strength and elasticity. People with straight hair have bonds that look like a ladder, while people with curly hair have bonds that look like a spiral staircase. We can manipulate these bonds with heat, water, and chemicals to change the shape or color of the hair. There are different bonds that respond to each of those different elements. When you see someone talking about Olaplex and they say it’s a bond builder, it means that the treatment rebuilds these bonds after they are broken by chemicals.

The outer layer is the cuticle and it looks like a roof or a snake with overlapping “scales” that naturally lay tightly against each other to create a barrier for the hair. Alkaline pH’s and heat can open these scales to allow color, deep conditioners, or chemical treatments to enter the cortex and change the natural color pigments or the structure of the bonds. When hair is damaged the cuticle doesn’t return to it’s tight formation, but instead, the layers stick up a little bit and catch on the hair around it. Each time you color your hair (particularly lightening it) the cuticle stays open a little bit more each time. You can help seal it back down with a product that has the pH of your hair and I always do this after a chemical service for my guests.

Now that you know all about the hair outside of your scalp, let’s break down what’s going on beneath your scalp! There are thousands of follicles on your scalp and these are what the hair sits in. The base of your hair has a little bulb that attaches to the follicle. Inside the hair bulb is the dermal papilla that is nourished by the blood vessel that connects to it and delivers oxygen and the hormones that regulate hair growth. Attached to the follicle is an oil (sebaceous) gland that produces the sebum that makes our hair appear oily if we haven’t washed it in a few days.

Remember how I said that hair isn’t dead? Here’s why: it would have to be living to begin with to be dead from weathering all the wear and tear we put it through. The protein of our hair grows from cells in the hair follicle. They work their way up through the follicle and while doing so, go through a process called keratinization where they are bulked up with keratin, the fibrous protein that makes up our hair. Once the cells are filled with keratin they continue moving upward, lose their nucleus and die. By the time the hair reaches the outside of your scalp, it is completely keratinized and is a nonliving fiber. See what I mean by “it would have to be living first?”

So that’s hair in a nutshell. I know it’s a lot of info, but I was just skimming the surface to help give you a better understanding of one of the most important parts of your look- your hair. I hope this was helpful and I love to write on topics that you want to read about. To give me suggestions, to get an answer to a question, or to request a specific topic you can email me at

I hope you have a great hair day!

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