Structure - Cuticle/Cortex/Medulla-Elasticity/Strength
All hair on the human scalp grows from a hair follicle. These
are placed at a slant in the dermis, or inner skin, and are the
thickest at the base where the follicle forms a bulb which contains
the dermal papilla attached to the follicle by the basal stalk.
Each strand of
hair contains three distinct layers. The cuticle of the hair is
made up of a single layer of scales which interlock with the cells
of the hair's inner root sheath to firmly anchor it in the follicle.
The cortex is composed of keratinized cells which are tightly
bound around each other. These fibril bands provide the hair with
strength. The medulla consists of large, loosely connected cells
with intracellular air spaces. By reflecting light these air spaces
determine the sheen and color tones of the hair.
Hair density on
the human scalp varies with the color and texture of the hair.
These differ as follows: blonde hair has an average of 140,000
hairs; brunettes or dark-haired people will average 110,000 hairs;
and red-haired individuals will have the least density with an
average of 90,000 hairs.
Attached to the hair follicle are the sebaceous (oil) and the
sudoriferous (sweat) glands. The sebaceous glands produce waste
by opening and closing continuously to release a waxy sebum oil
into the hair follicle and onto the scalp. The sudoriferous glands
contain many small structures with porous openings leading to
the skin. They produce substances which dry on the skin including
salts, acids, water secretion and bacteria. If not completely
dissolved and effectively removed from the scalp, they can help
cause severe itching and embarrassing dandruff.
The Causes of Hair Loss
The life of a scalp hair can range from one to six years. As a
result, everyone loses some hair each day. When a hair is released
from a hair follicle, a new hair should be regrowing from that
same follicle to replace the hair which was lost. The new hair
should be as thick and strong as the original hair it is replacing
with a growth rate of approximately ½" to ¾"
The onset of alopecia (baldness) is very gradual. As the hair
follicles begin to weaken, the loss-replacement process continues.
However, the new replacement hairs are much finer in diameter
and lighter in color than the normal hair previously lost. These
hairs, in turn, are replaced by even finer and lighter hairs until
all that remains are the almost invisible vellous hairs which
represent the final stage before baldness.
There are several
causes of hair loss which account for virtually all baldness.
Local and external problems are the easiest to control before
the onset of baldness. These causes vary including hygienic, traumatic,
infectious or medicinal. Among hygienic causes are dandruff, scaling,
severe itching and scalp tenderness. In these cases time becomes
very important because the conditions must be recognized and treated
in time before the hair follicles are permanently disabled. Genetic
factors vary because an individual does not inherit baldness as
such, but rather a predisposition to a weak follicular structure.
This predisposition may come from either the maternal or paternal
side of the family. General or acute diseases may influence the
scalp by changing its structure and interfering with normal function.
Certain internal medications may change the normal function of
the follicular structure which, as a result, may lead to excessive
How Your Hair
The growth of the hair depends mainly on the circulatory system
as fluids pass through the dermal papilla for two purposes: (1)
to supply the hair structure with nourishment; and (2) to remove
cellular wastes and other unwanted products. A strong circulatory
system is vital since the temporal and posterior branches of the
carotid artery bring nutrients and amino acids to the hair follicles.
A build-up of cellular waste seems to adversely impact the work
of the dermal papilla. Other contributing factors for normal hair
growth are the proper care of your hair and scalp as well as a
balanced and nutritional diet.
Hair growth is
achieved through cell division (mitosis) of the matrix cells of
the hair bulb in the anagen growing cycle of follicular development.
Cell mass increases and forces the hair cells to move into the
upper bulb. They harden or cornify to join other similar cells.
The mitotic activity of the cells and the synthesis of protein
within the matrix goes on as long as the hair is growing. However,
growth stops every one to six years and brings the onset of the
catagen transition cycle. The bulb will begin to degenerate and
all mitotic activity stops. Cells then go into the telogen resting
cycle for about three months. Fortunately, the dormant follicle,
unless problems are present, will then burst into anagen growing
activity once again and the overall production of hair resumes.