Hair Structure & Types Educational Chart
Comprehensive Guide to Hair Anatomy and Classification
Cross-Section View
🛡️ Cuticle (Outer Layer)
- Protective outer coating made of overlapping scales
- Composed of dead, flattened cells
- Protects inner layers from damage
- Reflects light = determines shine
- Damage leads to frizz and breakage
💪 Cortex (Middle Layer)
- Thickest layer (75-90% of hair)
- Contains melanin (hair color)
- Provides strength and elasticity
- Determines texture and curl pattern
- Where chemical processing occurs
⭐ Medulla (Inner Core)
- Central core of the hair shaft
- Soft, spongy tissue
- Not present in all hair types
- More common in thick, coarse hair
- Function still not fully understood
Characteristics:
- No natural curl or wave
- Lies flat against scalp
- Most reflective = shiniest
- Oil travels down easily
- Difficult to hold curls
Characteristics:
- S-shaped wave pattern
- More volume than straight
- Prone to frizz in humidity
- Can be straightened easily
- Holds curls moderately well
Characteristics:
- Defined spiral or ringlet curls
- Prone to dryness
- Less shine due to texture
- More volume and body
- Needs moisture to define
Characteristics:
- Tight, dense coils or zig-zags
- Most fragile hair type
- Naturally driest type
- High shrinkage (50-75%)
- Requires intensive moisture
| Factor | How It Affects Hair | Result |
|---|---|---|
| Follicle Shape | Round follicles = straight hair Oval follicles = wavy hair Flat/ribbon follicles = curly/coily hair |
Determines natural curl pattern |
| Follicle Angle | Perpendicular = straight down Angled = curves as it grows |
Affects direction and texture |
| Protein Bonds | Disulfide bonds link proteins in cortex More bonds = more curl |
Creates permanent curl structure |
| Cortex Distribution | Uneven cortex = one side thicker Causes hair to curl toward thinner side |
Determines tightness of curl |
| Sebum Production | Straight hair = oil travels easily Curly hair = oil can't travel down curves |
Affects moisture and shine levels |
| Cuticle Layers | Straight: 5-10 layers, flat Curly: 10-15 layers, raised |
Impacts shine and porosity |
| Genetics | Multiple genes control hair characteristics Curly genes often dominant |
Inherited from both parents |
🔬 Key Scientific Insights
Why straight hair is shinier: The smooth, round follicle allows cuticle scales to lie flat, creating a smooth surface that reflects light uniformly.
Why curly hair is drier: Sebum (natural oil) cannot easily travel down the twists and turns of curly hair, leaving the ends undernourished.
Why curly hair is more fragile: The bends and curves in curly hair create weak points where the hair is more prone to breakage under stress.
Why hair texture can vary on one head: Different follicles on the scalp can have slightly different shapes, leading to multiple textures.