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Transcript
Hair Structure - Hair Shaft
Layers of the Hair
It consists of:
1. Cuticle
2. Cortex
3. Medulla
Medulla
Cortex
Cuticle
1.The Cuticle
• The cuticle is the outside of the hair
shaft.
• It is made up of overlapping,
transparent scales which protect the
cortex.
• It is made of Hard Keratin & is usually
7 - 10 layers thick.
• The cuticle determines porosity of hair
Condition of the Hair
A perfect hair, its
cuticle intact, taken from
a newborn baby
Damaged cuticle
Condition of the Hair
Heated appliances soften the keratin of the hair. If they are too
hot, they can actually cause the water in the hair to boil, and
tiny bubbles of steam then form inside the softened hair shaft.
The hair is thereby weakened, and may break altogether.
2.The Cortex
• The Cortex is the largest and most
important layer and is made of hard
keratin
• Approximately 80% of hairs total mass
• Determines the texture and elasticity of
the hair
• Peptide, sulphur, hydrogen and ionic
bonds found here – these bonds allow us
to temporarily or permanently change the
shape of the hair.
• It is a complicated structure of parallel
twisted fibre; the appearance is similar
to a rope.
• These fibres of hard keratin are formed
from amino acids which are joined end
to end by Peptide Bonds.
• Strings of Polypeptide chains are linked
together by a cross bond called a
Di- Sulphide Bond
• All chemical and physical changes take
place in the cortex because this is where
all the bonds are found.
• The size of the cortex determines the
texture of the hair shaft.
• The elasticity of this layer enables the
hair to be physically re-arranged
• Melanin hair’s natural colour is in this
layer.
3. Medulla
• The medulla is found in the center
of the hair shaft.
• Not every hair has a medulla, it may
be continuous or broken along the
length of the hair shaft.
• The medulla is made of Soft Keratin
and sometimes it may contain
melanin.
The formation of the hair
follicle
• The follicle is a pocket in the
skin that the hair grows
from.
• The follicle grows through
the epidermis and into the
dermis.
• There are billions of follicles
all over the human body and
thousands over the scalp.
Structure of the follicle
• There are three main parts of the
follicle:
•
1. Papilla
•
2. The Germinal Matrix
•
3. The Hair Bulb
Papilla
• The papilla is found at
the bottom of the
follicle in the dermis. It
is shaped like the skin
is pushed up into the
bottom of the follicle.
• This is where the
blood capillaries pass
nutrients (food) and
oxygen into the cells
of the germinal matrix.
Germinal Matrix
• The germinal
matrix is inside
the follicle, above
the papilla, it is
full of cells that
are constantly
dividing.
• These cells join
together and
eventually become
the hairshaft
Hair bulb
• The hair bulb is
the name of the
lower part of the
follicle. It is
shaped like a light
bulb.
• This is where the
new cells start the
process of
keratinization
There are two other parts
of the follicle:
• 1. The Sebaceous gland is
attached to the side of the
follicle and has an opening
into the follicle.
• It is the oil gland that
secretes sebum into the
follicle. From the follicle
the sebum will eventually
coat the surface of the
hairshaft and the skin.
The Arrector-Pili-Muscle
• Is also attached to the side
of the follicle.
• It is described as an
involuntary muscle.
• When you get cold or
frightened it will contract
and pull the follicle upright.
This makes the skin at
the mouth of the follicle
bunch up causing what we
call ‘goose pimples’.