Hair life cycle

A hair is a specialized outgrowth of the skin epidermis.

 It has two distinct parts:

1- The hair shaft .

2- The hair follicle .

1. Hair shaft :

The part of the hair that can be seen above the scalp.

 It consists mainly of dead cells that have turned into keratins and binding material, together with small amounts of water.

Melanin inside cortex

 The cortex also contains melanosomes that contain the hair pigment melanin, produced when the hair was growing in its follicle.

 The melanosomes are carrying two types melanin:

 Eumelanin ( responsible for dark color of skin)

 Pheomelanin (responsible for the fair color of skin)

 A hair may contain just one type of granule or a mixture.

 Melanin loses its color when oxidized. Eumelanin is easily and faster oxidized than Pheomelanin

2. Cuticle:

Is more than just a protective layer.

Intact cuticle cells are smooth and glossy, and reflect light from their surfaces.

 Healthy cuticle makes the hair look healthy and attractive.

Weathering and damage:

The cuticle of the hair can be subjected to weathering or damage due to several factors:

 Thermal damage.

 Chemical damage during permanent coloring or straightening of the hair.

 Improper use of hair cosmetic and leaving the hair without conditioning.

Hair growth cycle:

 Hair growth occurs in cycles consisting of three phases:

Anagen (growth phase): Most hair is growing at any given time. Each hair spends 2-6 years in this phase.

 Catagen (transitional phase): 1-2 weeks, hair growth slows and the hair follicle shrinks.

 Telogen (resting phase): 2-4 months, hair growth stops and the old hair detaches from the hair follicle. A new hair begins the growth phase, pushing the old hair out.