The Biology Of Hair
Growth
Understand Your Hair Today!
There is nothing simple in our life. Even the hair growth
itself is very complex. Hair begins appearing on the human
body as early as when we are still in the womb. By the time
a developing fetus reaches 22 weeks old, there are already
approximately 5 million follicles on the body. It is an interesting
fact to know that, that is also all of the follicles that
will ever develop regardless of how long we live. None will
ever be added.
The Hair Anatomy
Hair consists of a follicle, which is rooted in the skin,
and the shaft of hair that appears on our body. The follicle
itself has multiple layers, and all of the layers have different
functions of their own. The papilla lies at the base of the
follicle. Capillaries are connected to the papilla and they
help to supply blood to the cells which surround the bottom
part of the hair strand called the bulb.
There are two sheaths surrounding the follicle, inner and
outer, they exist to both protect the hair shaft from damage,
and also to help it grow out in the proper direction. The
inner sheath runs next to the hair shaft and ends at the oil
(sebaceous) gland while the outer sheath runs to the gland
and ends at the erector pili muscle. This is also the muscle
that causes our hair to "stand on end" when it contracts.
The hair shaft is made up of three layers of dead protein
cells known as the keratin. The innermost layer, known as
the medulla, does not present hair shaft. The cortex, which
is the second layer, provides the bulk of the hair shaft.
As for the hair color, it is also determined by the pigmentation
contained in this layer. The outermost layer is known as the
cuticle. It is made up of a series of overlapping cells. The
hair's luster and sheen comes from the cuticle.
The Growth of Hair
Scalp hair grows at an average rate of six inches per year,
at the rate of only 0.3 – 0.4mm per day. Let’s
look at the three distinct stages of hair growth.
- Catagen Phase
This transitional phase lasts for about two to three weeks.
About 3% of your hair is always in this phase at any given
time. There is no hair growth during this period while the
out portion of the hair root sheath shrinks and attaches itself
to the root.
- Telogen Phase
This phase, which is also known as the "resting period"
is experienced by approximately 15% of your hair. Telogen
tends to last for around 100 days for scalp hair and much
longer for other body hair.
- Anagen Phase
This is a phase where the hair cells are experiencing the
activity of division and new hair growth occurs. This phase
can last for as long as two to six years. Shorter growth periods
are the signs to people who have trouble growing their hair
long.
The Hair Growth Disorders
Generally, there are two hair growth disorders affecting
humans, which are the hirsutism and hypertrichosis. Hirsutism
is a condition affecting mostly females. It is a condition
where excessive thick and dark hair growth is experienced
in areas typically reserved for males, such as the face, chest
and the areolae or area surrounding the nipple. As for the
hypertrichosis, it is a condition which causes excessive hair
growth in areas of the body where visible hair is not normally
present. Fortunately, both of these conditions can be treated.
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