Hair

A Few Basics

The hair our bodies produce is actually a protein called keratin. This compound is the same strong structural protein that an animals hoof, fur, and a birds feathers are made of. It is even the same protein that our finger and toe nails are made of.

A strand of hair has three distinct layers; an innermost layer called the medulla, which occurs in thicker terminal hairs; a middle layer called the cortex, which gives the hair texture and color; and a thin protective colorless layer, called the cuticle. Hair grows from the roots or follicles, which are saclike structures located just under the skin. At the base or lower end of a hair follicle is the hair bulb where the hair’s color pigment, or melanin, is produced. Blood vessels in the scalp provide nourishment for these hair follicles to grow.

On the average person the human scalp will have between 100,000 and 150,000 hairs. Each of the hairs on the scalp will have an independent life cycle; at any given time approximately 90 percent of scalp hairs will be in a growth phase and 10 percent will be in a resting phase. A growth phase, also called the anagen phase can last between four and five years before entering into a 2-3 week transitional period called the catagen phase. The final phase is a two to four month resting phase, or telogen phase. It's at the end of this resting phase that a hair falls out by being dislodged from the follicle by an emerging new hair.