Your Hair Has Layers: Understanding the Science Behind the Hair Fibre

av Melanin & Textures™ 26. oktober 2026

Your hair has layers. And no, we're not talking about your haircut!

Whether your hair is straight, wavy, curly or tightly coiled, every strand has an extraordinary internal structure that influences its strength, elasticity, colour and response to everyday styling.

Yet we often choose haircare products based on how our hair looks or feels without understanding what is happening beneath the surface.

At Melanin & Textures™, we believe that understanding the science behind your hair is one of the most empowering steps towards making informed haircare decisions.

So, let's take a closer look at the fascinating anatomy of a single hair fibre.

What Is the Hair Fibre?

The hair fibre, also known as the hair shaft, is the visible portion of hair extending beyond the skin's surface.

Although hair grows from a living follicle, the visible hair shaft consists of non-living, keratinised cells. This distinction matters because a hair fibre cannot biologically regenerate itself once it has been damaged.

The hair shaft has two principal structural regions and, in some strands, a third central region:

The cuticle: The protective outer layer.
The cortex: The keratin-rich structural core.
The medulla: A central region that may be present or absent.

Each contributes differently to the structure and behaviour of hair.

Scientific diagram of a hair fibre showing the cuticle, cortex and optional medulla — Melanin & Textures™ scientific illustration — schematic, not to scale.

1. The Cuticle: Your Hair's Protective Outer Armour

Imagine the overlapping tiles on a roof. That is a helpful way to visualise the arrangement of the hair cuticle.

The cuticle consists of flattened, overlapping cells that surround and help protect the inner cortex from physical and chemical stress.

Its condition influences several characteristics we associate with healthy-looking hair, including surface smoothness, shine, friction and manageability.

Scientific schematic illustrating the outer cuticle layer with overlapping protective cells — Melanin & Textures™ scientific illustration — schematic, not to scale.

What Happens When the Cuticle Becomes Damaged?

Repeated brushing, excessive heat, chemical processing and environmental exposure can gradually alter or wear away the protective surface.

When the cuticle becomes damaged, friction may increase, making the strands more susceptible to tangling and mechanical breakage.

An important distinction: rough-feeling hair is not always severely damaged. Product residue, humidity and other factors can also influence how hair feels.

The haircare connection: Gentle detangling, appropriate conditioning and minimising excessive friction can help preserve the hair's surface and improve everyday manageability.

2. The Cortex: Where Strength, Elasticity and Colour Live

Beneath the cuticle lies the cortex, which makes up most of the hair fibre.

The cortex contains organised keratin protein structures, associated proteins, chemical bonds and melanin pigments.

This region is responsible for much of the fibre's mechanical behaviour.

Scientific schematic of the keratin-rich cortex of human hair — Melanin & Textures™ scientific illustration — schematic, not to scale.

Strength and Elasticity

Hair contains keratin proteins organised into complex structures that help the fibre withstand everyday forces.

Chemical bonds, including disulfide bonds, contribute to its structural stability, while the organisation of keratin influences how hair stretches and recovers.

These properties help explain why chemical processing and excessive heat can change the way hair behaves.

Natural Hair Colour

The cortex also contains melanin pigments responsible for much of the natural colour of hair.

The amount, type and distribution of these pigments contribute to the wide variation in natural hair colours.

Can Damaged Hair Repair Itself?

This is where cosmetic science becomes especially interesting.

Because the visible hair shaft is non-living, it cannot biologically heal itself in the same way that living skin tissue can.

However, appropriately formulated conditioning products can improve softness, lubrication, combability and the appearance of damaged surfaces.

Certain formulations can also temporarily improve or modify particular physical properties of damaged hair fibres.

The important distinction is between improving the condition and performance of hair and claiming to restore it completely to its original, undamaged structure.

3. The Medulla: The Centre That Isn't Always There

At the centre of some hair fibres lies the medulla.

This region has a less organised structure than the cortex and may contain loosely arranged cells and air spaces.

Interestingly, the medulla is not present in every hair strand.

It may be continuous, fragmented or absent, and is more commonly observed in thicker hair fibres.

Longitudinal educational illustration comparing continuous, fragmented and absent medulla in hair fibres — Melanin & Textures™ scientific illustration — schematic, not to scale.

Although it is part of hair anatomy, the medulla contributes relatively little to the mechanical strength of the fibre compared with the cortex.

Did you know? A strand without a visible medulla is not automatically damaged or unhealthy. It can simply reflect normal structural variation.

Why Does Hair Structure Matter for Textured Hair?

For curly, coily and tightly textured hair, understanding fibre structure is especially valuable.

Curvature, fibre geometry and grooming practices influence how mechanical forces act on individual strands.

Repeated manipulation and friction can contribute to damage, particularly when the hair is already chemically processed or weathered.

This does not mean textured hair is inherently unhealthy or that every curl type requires the same products.

Instead, it highlights the importance of understanding your hair's individual characteristics, processing history and everyday needs.

A thoughtful routine considers:

Surface condition: Is the hair tangling easily or experiencing excessive friction?
Mechanical stress: Are brushing, detangling or hairstyles placing unnecessary tension on the strands?
Chemical and thermal history: Has the hair been relaxed, bleached, coloured or repeatedly exposed to high temperatures?
Conditioning performance: Do your products improve slip, softness and manageability without excessive build-up?

Rather than chasing a perfect hair type or an endless collection of products, the goal is to make informed choices based on how your hair actually behaves.

What Haircare Products Can — and Cannot — Do

Understanding the hair fibre also makes it easier to evaluate cosmetic claims.

Conditioners, oils, leave-in treatments and other haircare formulations can offer valuable benefits, depending on their ingredients and overall formulation.

They may help reduce friction, improve combability, increase softness and support the appearance and manageability of weathered hair.

However, cosmetic products cannot make the existing hair shaft biologically regenerate. The effects of conditioning treatments also vary and may diminish with washing, environmental exposure and further grooming.

This is why prevention, appropriate conditioning and realistic expectations remain important elements of hair-fibre care.

The Takeaway: Science Meets Haircare

Your hair is more than what you see in the mirror.

Beneath every curl, coil, wave and straight strand lies an intricate structure that influences how hair responds to grooming, products and the surrounding environment.

The cuticle protects. The cortex provides much of the strength, elasticity and colour. And the medulla? Not every strand has one.

Understanding these differences helps us move beyond haircare myths and towards more informed decisions.

At Melanin & Textures™, we believe good haircare begins with understanding.

Because confidence grows when care is guided by knowledge.

Confidence Through Care™

Continue Exploring Hair Science

Deepen your understanding with these related articles from The Journal:

Scientific References

Yang, F.-C., Zhang, Y. & Rheinstädter, M. C. (2014). The structure of people's hair. PeerJ, 2, e619. https://doi.org/10.7717/peerj.619
Fernandes, C., Medronho, B., Alves, L. & Rasteiro, M. G. (2023). On hair care physicochemistry: From structure and degradation to novel biobased conditioning agents. Polymers, 15(3), 608. https://doi.org/10.3390/polym15030608
Weiand, E., Rodriguez-Ropero, F., Roiter, Y., Angioletti-Uberti, S., Dini, D. & Ewen, J. P. (2025). Understanding and controlling the friction of human hair. Advances in Colloid and Interface Science, 345, 103580. https://doi.org/10.1016/j.cis.2025.103580
Understanding breakage in curly hair. (2015). British Journal of Dermatology. https://pubmed.ncbi.nlm.nih.gov/26207659/