Structure of Black Hair

Hair is mostly made of a protein called keratin. Fingernails and the top layer of skin are also made of keratin protein. Each strand of hair consists of three layers.
1. An innermost layer or medulla.
2. The middle layer is the cortex. The cortex provides strength, color, and the texture of hair. 
3. The outermost layer is the cuticle. The cuticle is thin and colorless which protects the cortex.

The center of the hair is called the cortex. It makes up 80 percent of Indian hair. It's made of small fibrils that twist together to make the longer fibers stronger. The cuticle is made of dead cells that overlap each other in several layers. The condition of the cuticle plays a part in the appearance of the hair. If the dead cells lay closely together (closed cuticles) then the hair looks shiny and healthy, however, if they lift up (open cuticles) the hair appears dull, dry, and tangles easily.

Medulla cells contain air pockets that are found inside the hair shaft which form the medullary canal. Lipids, a fat substance, is passed through to the cortex or cuticle from the medulla cells. Layers of lipids are formed to bind moisture and protein to the hair shaft. African American hair consists of 88% protein, 10‐15% water, 5‐10% pigments, minerals and lipids. The cortex and cuticle are formed from solid keratin fiber and the binding material is formed from amorphous keratin, which fills in the spaces inside the cortex and cuticle. The amorphous keratin holds the fibrous structure together and keeps it elasticity.

Structure of the hair root

Beneath the surface of the skin is the root of the hair, which is enclosed within a hair follicle. At the base of the hair follicle is the dermal papilla. The dermal papilla is fed by the bloodstream which nourishment the new hair produces. The dermal papilla is essential to hair growth because it contains receptors for androgen and male hormones. Androgen regulates hair growth.

The Hair Growth Cycle

Hair follicles grow in repeated cycles. A cycle can be broken down into three phases:

Anagen ‐ Growth Phase

Catagen ‐ Transitional phase

Telogen ‐ Resting Phase Each hair goes through the phases independent of the neighboring hairs.

The regeneration of hair is influenced by many factors:

• Health
• Hereditary factors
• Diet
• Hormone balance
• Age
• Physical condition
• Climate
• Chemical effects
• Sex
• Effects of disease