| Hair Growth |
| Karen Marie Shelton |
| Revised Date: 01/17/07 - Original Publication Date: 6/23/00 |
Introduction
Except for certain circumstances, human hair is always either in
the process of growing or falling.
Depending on which hair expert you consult, most
humans lose between 75 and 150 hairs per day on a
routine basis.
Hair growth cycles are controlled by a variety of
factors which may include:
- Daily diet and levels of nourishment
- Seasons of the year
- Time of day - daylight versus night time
- Location of the hair on the body (head or
otherwise)
- Race
- Heredity
- Age
- Sex
- Environment
- Sleep patterns
- Existence of certain types of diseases
- Chemotherapy
- Fluid consumption
Hair on the head grows at a different rate than hair
on the face, arms and legs or other parts of the body.
Scalp hair generally grows at the rate of 1/2 inch
per month. There are exceptions to this rule
depending on a wide range of factors.
Hair Growth Mechanics
So how does hair really grow? It's one of those amazing
miracles of the human body.
The actual growth spot for hair is attached somewhere
within the hair follicle near the intersection with the
papilla, which is the base of the follicle.
As hair proceed through its natural aging cycle, it
eventually loosens and slowly breaks away from the
papilla.
The old hair is firmly held to the sheath that
surrounds it and gradually moves upwards towards the
surface of the skin.
When the aging hair is still a short distance from
the papilla, a column of cells is automatically sent
down towards the papilla. This group of newly
released cells is the trigger of the spark that begins
the generation of a new hair within the same follicle
with the aging strand.
The new hair bulb, in its growth from the vital
strand within the follicle, grows downward towards the
papilla of the aging hair. Contrary to popular
belief, the new replacement hair bulb grows down to the
papilla, not up from it.
Eventually, once the new hair is firmly implanted
into the papilla, it does begin to grow upwards towards
the skin's surface. As the new hair grows upward,
it gradually pushes the old hair out.
At some the original hair becomes loosened from the
walls high up in the follicle and is dislodged
completely in a number of ways. The hair can be
brushed, combed or pulled out.
Or it may come out
during the washing process, during sleep or just fall
naturally. Some people have reported their old
hair appears to just pop out.
New Hair Appearance
In some cases new hair may not appear immediately after the old
hair has been shed.
A new hair will appear if the vital strand of cells
was successfully deposited by the former hair. As
long as the growth process continues its normal cycle,
all is well and new hair will continue to appear.
In normal circumstances the rate of hair replacement
keeps pace with the rate of hair loss. Problems do
occur when the strands of hair growth cells are not
deposited by old hair in order for new hair to be able
to replace it.
It is very important to note that hair can only be
formed by hair. Just like epidermic (skin)
structures can only be produced by other epidermic
structures.
Because the papilla in the hair follicle is not an
epidermic structure, it cannot give rise to hair.
The papilla's main role is to nourish the hair.
The influence of the papilla on regeneration of hair
has been at times misrepresented by some experts. |