The Hair Shaft
Your hair shaft is composed of three basic layers: the cuticle, the cortex, and the medulla. This shaft makes up everything about your hair, from how smooth or frizzy it is to the color to the shape. So let’s unravel each layer, and what they’re for.
The Cuticle
The cuticle is the outermost layer of a hair strand. Under a microscope, it appears to have overlapping scales (like those of a fish). These translucent scales protect the rest of the strand from damage. Ideally, we want the cuticle to be lying flat, with the scales tight to the cortex (more on that below). With damage, age, or drier hair types, the cuticle scales can become lifted, leading to more breakage, split ends, and frizz.
The Cortex
The cortex the middle layer of a hair shaft, and the thickest, made up of long strands of keratin spindles. It’s responsible for your hair’s color, whether you’re rocking your natural pigment, or you’ve dyed your hair. It’s also what gives your hair its shape, from straight to curly and coily.
The Medulla
The medulla is at the very center of your hair… if it’s there. Some strands have it, some strands don’t, and the thicker the strand, the more likely you’ll find a medulla in it. The truth is, we actually don’t know exactly what the medulla does, but there’s speculation that it has something to do with moisture. There are still some mysteries left to be solved!
Want to know more about what makes your hair, your hair? Learn more about the science behind the strands at our Tips & Tricks.
About HairCode, backed by decades of hair care research and industry-leading cosmetic scientists
We're obsessed with hair and the science behind what makes it look and feel amazing. Our dedicated team leverages years of extensive haircare research and product development led by pioneering cosmetic scientists, PhDs in Biology and Chemistry, along with esteemed professional hair stylists from around the globe. Our goal is to be the most accurate and easy-to-use platform for you to learn about your hair. Our HairCode Quiz is built to harness a wealth of haircare research to give you a straightforward and science-backed haircare regimen recommendation based on questions that matter. We know that hair can be complicated. That's why we break it down for you piece by piece with your unique HairCode. So, let's get to the root of it... Because we are here to support you on a journey of self-discovery and love for your hair.
