Let’s talk more about hair. Here is more information on the science of hair.
Functions of Hair
The reasons we have hair, and the functions of its growth patterns, are not completely understood. Our prehistoric ancestors were much hairier than we are today; the reason for the decreased hairiness of modern man is unknown, although it is reasonable to assume that it parallels the use of clothing for warmth and protection from the sun and physical trauma. Hair is integral to our body image and can have a profound influence on our self-esteem and self-confidence. There is no other part of the human anatomy that can be changed or manipulated so easily. Hair can be groomed, styled, waved, straightened, dyed, braided, or cut, and, unlike tattoos or body piercing, changes made to our hair can be completely reversed. Hair serves as an important means of self-expression, and the loss of this form of self-expression in those going bald may account, at least in part, for the despair that they may experience.
Hair is simple in structure, but has important functions in social functioning. Hair is made of a tough protein called keratin. A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. In the hair bulb, living cells divide and grow to build the hair shaft. Blood vessels nourish the cells in the hair bulb, and deliver hormones that modify hair growth and structure at different times of life.
Each hair follicle measures about 3-4 mm in length and produces a hair shaft about 0.1 mm in width. The hair follicle has five main parts. Starting from the bottom of the follicle, they are; the dermal papillae, matrix, outer root sheath (ORS), inner root sheath (IRS), and the hair shaft.
Hair growth occurs in cycles consisting of three phases:
- Anagen (growth phase): Most hair is growing at any given time. Each hair spends several years in this phase.
- Catagen (transitional phase): Over a few weeks, hair growth slows and the hair follicle shrinks.
- Telogen (resting phase): Over 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.