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Hair Structure & Growth
hair structure
hair growth
hair life cycle
Basic Hair Structure
This diagram shows the three layers of a
hair follicle, the cuticle, cortex and
medulla.
The cuticle is made up of scales and is
translucent (the hair colour shows through it).
It has a protective function.
The cortex forms the bulk of the hair and
it is in this part of the hair that the
chemical changes of perming and neutralising
take place.
The medulla is an air space in the middle
of the hair and may not always be present .
Hair Growth
There are two main type of hair on the human body;
•
Fine vellus hair which grows on the body.
•
Stronger terminal hair which grows on the scalp
and makes up eyebrows, eyelashes, beards and moustaches.
However there is a third type of hair, lanugo hair, it is only found on
human foetuses and is even finer than vellus hair.
Hair Growth
The scalp ( and skin) is divided into two layers:
The outer layer – the epidermis –
is the outer protective layer of skin.
It is constantly shedding itself,
losing dead skin cells. When this happens
excessively on the scalp it is known
as dandruff.
The inner layer – the dermis –
is the thickest and most
important part of the skin.
It is where you will find;
epidermis
dermis
Hair Growth
Hair is made of the protein keratin, all proteins are made up of amino acids.
The hair you see emerging from the scalp is dead, it does not hurt when we cut
through it, or when chemicals such as perm lotions or bleaches are put onto it.
But at the base of the follicle the hair is alive and growing, that is why we can
feel someone pulling our hair because it is attached to the scalp by its roots,
sitting in tiny pockets called the hair follicle.
The sebaceous gland is also attached to the
hair follicle and produces sebum, the hair’s
natural oil. The sebum flows around the hair
root and outwards onto the scalp surface.
If too much sebum is produced, the scalp
and hair will be too greasy, but if too little
sebum is produced the hair and scalp
will be too dry.
The erector pili muscle is
attached to the hair root and
contracts to pull the hair upright,
creating the goose pimp
The heart pumps blood containing food and oxygen ( needed to make new keratin)
through our arteries towards the skin surface. The arteries become small blood capillaries
in the dermis, where they supply into the bottom of the hair root or follicle to feed the dermal papilla.
The more blood flowing towards the hair papilla, the more the hair will grow.
hair life growth cycle
Hair growth needs energy to grow. The papilla oxidation of glucose provides that energy. The
blood in turn supplies oxygen and glucose to the papilla. Hair grows from the bottom of its root at
the dermal papilla, where new cells are constantly being produced. These soft cells become
hardened to form strong hair above the skin surface. The average rate of hair growth is 1.25 cm.
The growing stage of the hair is called the anagen stage. When the hair starts to go into
its resting stage, it is said to be in the catgen stage. The resting stage is called the
telogen stage
Anagen
Catagen
Telogen
Active growth 1-7 years
(average 3 years)
Breakdown
And change
2 weeks
Resting Stage
3-4 months
The only way to improve the condition
of the hair permanently is through
the blood supply to the papilla
Anagen Regrowth
The thickness, shape and
texture of the hair is
determine at this stage