When I was little, I would always look at my mom’s curly hair and wish my hair was like hers instead of being boringly straight. And this got me thinking, why did I have straight hair when she had curly hair? I mean, even my dad’s hair is a little wavy! So what is responsible for this difference between my hair and my parent’s hair; what causes different types of hair?
So many things apparently
I started looking into this a month ago, and I’m still reading about different factors that affect the type of hair you have: your follicles, the keratin in our hair, and genetics. But then, genetics is its own fountain of knowledge, where several of its drops contribute to our hair type. In other words, there are several different genes (and by several, I mean a lot) that affect whether we have straight, wavy, curly or frizzy hair. So I’m going to start with a simple factor for now, the follicle, and explore keratin and the genetics of hair at a different time.
The Role of Follicles in Hair Types
The shape of the follicles of our hair is a factor, as it dictates the shape our hair strands will take. The two shapes of follicles are circular and elliptical. There are several sizes of ellipticals, each of which gives rise to wavy, curly or frizzy hair, shown below.
This image is a little bit deceiving though; we know that there is more to the follicle than just the hole that hair grows from. Recall that there are two components to the follicle; the papilla and the bulb. The bulbs of your hair follicles are the components that actually determine the texture of hair you have. So while the tube itself is either circular or elliptical, it is more important for us to note what shape the bulb is. If the bulb is spherical, it will result in straight hair (even if the follicle tube looks like it’s elliptical)!
The presence of a hook is also a factor for the type of hair you have. By hook, I mean that the bulb sits at an angle. If you look at the images below, the follicle on the left is pretty straight as the bulb sits 90 degrees to the imaginary horizontal line (depicted in yellow)
The follicle on the right, however, shows that the bulb is sitting on an angle to the horizontal line. This causes some of the keratin molecules on one side of the follicle to be closer together than the other side, creating a curl.
And that’s all there is to know about the role of follicles in making hair curly or straight.
Next week: We’ll talk about what role keratin plays in determining hair type!
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Bernard B.A. 2003. Hair shape of curly hair. Journal of the American Academy of Dermatology: 48S120–S126. September 19, 2013.