The Science of Hair

Hair Anatomy: Composition & Structure

Hair is often approached cosmetically — shine, thickness, softness.
Yet biologically, it is a complex protein structure emerging from a living mini-organ beneath the scalp.

To care for hair intelligently, one must first understand its anatomy and composition.

At Hérbönise, formulation begins with structure.

 

What Is Hair?

Hair is a filament composed primarily of keratin, a fibrous structural protein produced within the hair follicle. Each strand originates from a dynamic biological structure embedded in the scalp.

There are two distinct components:

• The hair shaft — the visible fiber above the scalp
• The hair follicle — the living structure beneath the skin

The shaft is biologically non-living tissue.
The follicle is metabolically active and responsible for hair growth, thickness, and cycle duration.

Hair growth follows a cyclical biological rhythm, and its protective functions extend beyond aesthetics — subjects we explore in dedicated article The Hair Growth Cycle within The Science of Hair section.

True hair health begins at the follicular and scalp level.

 

Hair Anatomy: Understanding the Structure of the Hair Shaft

The hair shaft consists of three concentric layers. Each plays a distinct structural role.

1. Cuticle – The Protective Barrier

The cuticle is the outermost layer of the hair fiber.

• Composed of overlapping scale-like cells
• Acts as a protective shield
• Controls smoothness and light reflection
• Regulates moisture exchange

When the cuticle lies flat, hair appears smooth and luminous.
When disrupted — through heat, friction, or chemical exposure — hair becomes porous, dull, and prone to breakage.

Maintaining cuticle integrity is essential in preventing structural damage.

 

 

If the cuticle is damaged, the cells of the cuticular layer are ‘open’; they do not overlap as they should, and they can start to break off. In this case, the hair loses its sheen and the ends of the hair become f rayed and split. The main purpose of the cuticle layer is protecting the cortex against outside factors that cause hair damage, such as heat, styling, chemical stressors, etc.

 

2. Cortex – The Structural Core

The cortex forms the bulk of the hair strand.

• Composed of tightly packed keratin fibers
• Contains structural lipids
• Houses melanin (natural pigment)
• Determines strength, elasticity, and texture

Damage to the cortex compromises tensile strength, leading to split ends and fiber fragility.

The cortex is where hair retains memory — of heat styling, chemical processing, and mechanical stress.

 

3. Medulla – The Central Canal

The medulla is the innermost layer of the hair shaft.

• More prominent in coarse or thick hair
• May be absent in fine hair types
• Less critical to structural integrity

 

The Hair Follicle: The Living Origin of Growth

Beneath the scalp lies the hair follicle — a sophisticated biological structure often described as a “mini-organ.”

Key components include:

·         Dermal Papilla – supplies nutrients and growth signals

·         Matrix Cells – rapidly dividing cells that form new hair

·         Sebaceous Gland – produces sebum (natural scalp lipid)

·         Arrector Pili Muscle – responsible for follicular contraction

The follicle determines:

• Hair thickness
• Growth rate
• Density
• Hormonal sensitivity (including DHT response)

Understanding the follicle is central to addressing hair thinning and shedding.

 

Composition of the Hair Fiber

The hair shaft consists of:

• Keratin Protein - 80–85%
• Water - 10–15%
• Structural Lipids - 1–9%
• Pigment (Melanin)
• Trace elements

Keratin chains are stabilized by disulfide bonds, which give hair its strength and shape. These bonds are altered by chemical treatments and high heat exposure.

Lipids within the hair fiber support flexibility and reduce friction between strands.

Preserving these structural elements is fundamental to maintaining resilience.

Pigment (melanin) is located in a thin membrane that separates macrofibrils in the cortex. Melanin is responsible for the color of the hair.

 

Why Hair Anatomy Matters in Haircare

Understanding hair anatomy and structure changes how we approach intelligent haircare.

• The shaft cannot regenerate once damaged.
• The follicle responds to internal and scalp conditions.
• The cuticle determines visible surface quality.
• The scalp regulates the environment of growth.

Intelligent care therefore prioritizes:

1. Protecting cuticle integrity
2. Supporting scalp balance
3. Reducing structural stress
4. Reinforcing lipid layers

This is the foundation of botanical precision.

 

From Structure to Ritual

Botanical oils function by:

• Reducing surface friction
• Supporting cuticle alignment
• Reinforcing lipid barriers
• Improving mechanical resilience

They do not “feed” the hair shaft — but they can protect it and support the scalp environment in which growth occurs.

When science informs ritual, care becomes intentional.

Hair is not merely aesthetic.
It is biological architecture.
And structure deserves respect.

 

Conclusion

Hair is a structured keratin fiber emerging from a living follicular system governed by biological cycles and scalp equilibrium. Its strength, elasticity, and appearance are determined by microscopic architecture.

Understanding hair anatomy is the first step toward preserving structural integrity.

This is where knowledge becomes ritual.
This is where structure informs formulation.

This is the science behind Hérbönise.

The Hair Growth Cycle

Hair growth follows a cyclical biological pattern known as the hair growth cycle.

Anagen (Growth Phase)

• Lasts 2–7 years
• Determines maximum hair length
• 85–90% of scalp hair is in this phase
  

 

Catagen (Transition Phase)

• Short transitional period (~2–3 weeks)
• Follicle shrinks
• Growth activity slows

Telogen (Resting Phase)

• Lasts approximately 3 months
• Hair sheds naturally
• New Anagen hair replaces it

Shedding 50–100 hairs daily is physiologically normal.

Disruption in this cycle — whether due to stress, hormonal shifts, inflammation, or nutrient deficiency — may increase visible shedding.

 

 

The Biological Functions of Hair

Hair serves several essential physiological purposes.

1. Protection

• Shields the scalp from UV radiation
• Reduces environmental stress exposure
• Provides minor physical barrier protection

 

2. Thermal Regulation

Hair assists in temperature modulation by:

• Providing insulation
• Reducing heat loss
• Creating airflow buffering at the scalp surface

 

3. Sensory Function

Hair follicles are surrounded by nerve endings.
Even subtle strand movement stimulates tactile signals.

Hair is part of the body’s sensory system.

 

4. Sebum Distribution & Lubrication

Sebaceous glands produce sebum, a natural lipid that:

• Coats the hair shaft
• Reduces mechanical friction
• Maintains flexibility
• Supports cuticle smoothness

Balanced sebum production is essential for scalp equilibrium.