Hair Structure and Hair Life Cycle

Basic Hair Structure

Men’s hair is composed of structural and strong protein that is called keratin. This is the protein that is responsible for the existence of your nails and the outer layer of your skin.
Each fibre of hair consists of exactly three layers:

1. First there’s the innermost layer (aka medulla) which is only present in large and thick hairs.
2. The second , middle layer , is known as the cortex and provides strength , color and texture of your hair.
3. The third , outermost layer, is known as the cuticle. It is thin and colorless and serves as a shield of the cortex.

Structure of the hair root

The hair root is placed below the surface of the skin and is enclosed within a hair follicle. The dermal papilla is situated at the base of the follicle and is fed by the bloodstream which carries nourishment to produce new hair. The dermal papilla is one of the most important structures when it comes to hair growth because it contains the most important receptors – those for male hormones and androgens. Androgens regulate hair growth and in scalp hair Androgens may cause the hair follicle to get progressively smaller and the hairs to become finer in individuals who are genetically predisposed to this type of hair loss.

Deeper Look In The Hair Growth Cycle

What is typical for hair follicles is that they grow in repeated cycles. If we take a deeper look at those cycles , each of them can be broken down into three main phases:

1. First phase – Growth Phase – Anagen
2. Second phase – Transitional phase – Catagen
3. Third phase – Resting phase – Telogen

There is one interesting fact about those phases - each hair passes through them independent of the neighboring hairs.

Anagen Phase - Growth Phase

Scientists have calculated that approximately 85% of all hairs are in the growing phase all the time. This so called Anagen phase or growth phase can vary from 2 to 6 years. The average growth of hair is 10 cm per year and it’s unlikely that any hair will grow more than one meter long.
Catagen Phase - Transitional phase

When the Anagen phase comes to an end the hairs enters the Catagen phase which is usually lasting about one or two weeks. While the Catagen phase is in progress the hair follicle shrinks to about 1/6 of its normal length and its lower part is destroyed. Then the dermal papilla breaks away to rest below.

Telogen Phase - Resting phase

The Telogen phase (aka resting phase) follows the Catagen phase and usually lasts about 5 to 6 weeks. During this time the hair isn’t growing but it stays attached to the follicle. The dermal papilla stays in a resting phase below. Scientists believe that between 10 and 15 % of all hairs are in the resting phase at one time.

The cycle is starting all over when at the end of the Telogen phase the hair follicle re-enters the Anagen phase and the dermal papilla join with the base of the follicle. When this happens new hair begins to form and if the old hair hasn’t already been shed the new hair pushes it out and the growth cycle starts from the beginning.