Hair Growth
Although way back in pre history man's hair covering may have had a more
functional purpose, such as protecting the skin from damage, and
insulating the body from the vagaries of weather, modem man's scarcer
covering of hair offers little of these properties. Aside from hair in
the pubic regions, which of course signifies sexual maturity in both
sexes, hair, especially hair on the head, seems to be of little
practical use.
However we do seem to instinctively appreciate a full, healthy head of
hair. We find it aesthetically pleasing, and judging by the many
millions of pounds spent by consumers of both sexes each year on hair
care products, the condition of our head hair is of considerable
importance to us.
Growth Cycle of Hair
The observable part of each head hair above the skin surface is known as
the hair shaft. It is composed of a material called keratin, made up
entirely of dead protein. The living part of each hair is situated below
the skin surface in a small cavity known as a hair follicle.
There are three basic types of head hair. The first, lanugo hair, is to
be found only on a human foetus, and is replaced Hair Point before birth
by the second type, the very fine vellus hair. This is replaced in turn
by the third and final stage, terminal hair, which is the mature hair
shaft. During puberty the vellus hair covering of other bodily areas,
such as in the pubic regions, also change into terminal hair.
Though terminal hair is the final stage head hair reaches, it should be
noted that most of our body hair remains in the vellus stage. To give an
example; the very fine 'down' barely discernible on a woman's face that
softens her features.
The normal growth cycle of head hair consists of a number of stages. The
period of active growth during which a hair may continue growing from
between two to seven or so years is the anagen stage. The anagen I stage
produces downy hair of the vellus kind. During the anagen 2 stage, the
hair continues to grow to maturity, in other words it develops into the
coarser appearing terminal growth. The length of hair that a person may
achieve is directly related to the length of activity of the anagen
stage.
After the anagen stage, the root of the hair becomes detached from the
follicle, thereby curtailing any further growth. The follicle itself
contracts during this period. This is known as the catagen phase, and
will last for two weeks or so.