Role of Hair and Structure of Hair
Despite the important role of hair in protecting you from your
environment (cold, heat, the sun's rays), you are probably most aware of
its impact on your appearance. Social norms dictate how much hair is
acceptable and where it is acceptable on the body For instance, short
hair may be one year and out the next. The hair care industry is
thriving and it brings with it annual trends in hair styles and hair
care products. In North America today, it is not acceptable for women to
have hair in the armpits or on the legs, whereas in the 1960's this
trend was partially reversed, as the style of the day focused on the
natural look. Men with hairy chests are considered masculine but even
this is subject to socially acceptable limits.
Hair is an integral part of the structure of your skin and, like your
skin, it changes with the passage of time. A single strand of hair is
made of several components: the hair shaft (the visible part of the
hair) is dead; the hair follicle (sac) and the portion of the hair below
the skin's surface is a single structure which lives and grows at an
average rate of I to 3 centimeters (1/2 to 1 inch) per month. The hair
follicle is an appendage of the epidermis of the skin. It extends into
the dermis, from which it receives its blood supply and sensitivity
through the surrounding network of nerves.
Hair develops in three phases: a growing phase, a transition phase, and
a resting phase during which the hair is shed. On average it takes a
single scalp hair one to two years to pass through all three
developmental phases. Although you shed hair every day, it grows back at
about the same rate as you lose it. An adult has an average of about
100,000 head hairs and they are lost and replaced at a rate of
approximately 100 hairs a day, under normal conditions. Hence the hairs
which are found on the shower floor and tangled in hair brushes each day
Hair also tends to grow faster in the summer than in the winter.