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By Chrys Antoniou
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Melanocytes are developed from special
nerve tissue in the embryonic stage of
development of human life.
This nerve tissue is located in an area called the neural crest which is also responsible
for the nervous systems sympathetic,
parasympathetic and sensory nerves. It is
also found in the ears,eyes,mucousmembranes hair and skin
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Where are they found?
Melanocytes are found in the stratum
germinativum layer of the Epidermis also
known as the Basale layer.Melanocytes contain melanosomes which
carry little packets of pigment called
melanin into the surrounding keratinocytes.
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Melanocytes are pigment carrying cells.
They have a dendritic shape which means
they have arms, rather like an octopus
These arms carry pigment(melanin) throughtheir denrites into surrounding keratinocytes
The melanin is passed to the keratinocytes
through a process called phagocytosis, that is
the keratinocytes bite off the end of thedendritic arm to gain access to the melanin
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It has also been suggested that the dendrites
inject the melanin into the surrounding cells.
This seems much more civilised
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More Facts
We have 1 melanocyte to every 36 keratinocytes
The concentration of melanocytes varies around
our body.
On the head its around 1,930 and on the foot it isconsiderably more, around 2,840.
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Light is part of the electromagnetic spectrum
It is a form of energy which comes in energy
parcels or photons
Photons travel in waves Waves can be long or short
The distance between the top of the waves is
a measure of their intensity (energy)
The closer the top of the wave the more
energy per photon (or parcel)
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Causes damage to chemicals, cells and
tissues
Triggers a defensive response by: Thickening of the epidermis (hyper
proliferation of keratinocytes)
Hyper activity of the melanocytes (tanning)
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Increased production of more melanin-
coated melanosomes.Greater protection to the underlying
chemicals, cells and tissues.
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To blood cells and endothelial (outer) linings
Collagen and Elastin (fibrous proteins)
Fibroblasts and mast cells(white blood cells)Nerve cells and receptors
Langerhans cells of the Immune system
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Due to their higher melanin content and
their shape and distribution of melanosomes
darker skins absorb 70% of UV
Light skins absorb only 25% Light skins reflect around 60% of uv rays
where as in dark skins it is only 25%
Only 5% of UV that penetrates the horny
layer of dark skin goes as deep as thepapillary layer of the dermis as opposed to
15% with light skin.
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M.E.D = minimal erythemal dose
Minimal erythemal dose is the amount of
time your skin takes to go pink/red in the
sun without any sun protection. The average M.E.D is 6-10minutes
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Even though only a very small amount of UVB
hits the surface of the earth the erythema
effect on the skin is high
With UVA, the sun predominantly hits thesurface of the skin and the erythema effect
is only produced when exposed to very high
amounts.
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Skin type Typical Features Tanning abilityI Pale white skin,
blue/hazel eyes,
blond/red hair
Always burns, does
not tan
II Fair skin, blue eyes Burns easily, tans
poorlyIII Darker white skin Tans after initial
burn
IV Light brown skin Burns minimally,
tans easily
V Brown skin Rarely burns, tans
darkly easily
VI Dark brown or black
skin
Never burns, always
tans darkly
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Med can happen through:
Short exposure to UVB
Long exposure to UVA
Skin develops a delayed erythema withinhours. It is an inflammatory response from
chemicals released from cells that are
damaged.
Sunburn is noticed hours before it is actuallyfelt-there is a time delay
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Effects on keratinocytes and melanocytes
can be long term even after just one M.E.Dexposure
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Infections
Medications
Connective tissue disorders e.g. rash,
eczema etcHarsh skin care products
Waxing, massage (tapotement),facial
massage
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Response to sunburn:
6hrs- dramatic reduction in Stratum
Germinatum (basale layer) mitosis
72 hours- acceleration of mitosis Days- mitotic rate gradually decreases
(healthy cells are being formed)
Weeksmitosis returns to normal
A SINGLE SUNBURN CAN TAKE UP TO 6 WEEKS
TO RECOVER FROM!
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2x to 3x increase in number of keratinocytes
(to carry more melanin)
Increased Epidermal thickness (hyper
proliferation) Protective blanket over Basale cell,langerhan
cells and Dermis
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Increase in number and length of dendrites
Increase in melanosome production
These result in Delayed Tanning (DT) which is
long lasting
Immediate tanning (IT) is when the existing
melanosomes darken. This only lasts a fewhours and fades
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Physical- work by reflecting light
E.g.: Zinc Oxide and Titanium Dioxide,
(broad spectrum ,UVA and UVB)
Chemical-Absorbs and neutralises UVA andUVB rays
E.g.: Avobenzone (parsol 1789),(uva &B)
Octinoxate(UVB), octisalate(UVB),
oxybenzone (UVB and UVA up to 350nm)
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Photoageing- premature ageing of the skin, lineswrinkes,loss of firmness and density
Solar elastosis-break down of Elastin causingvertical creases in the skin and wrinkles
Epidermal thickening-uneven skin surface, roughand dull looking
Hyperpigmentation-dark patches e.g. solarlentigos, melasma(chloasma),solar keratosis
Hypopigmentation-loss of pigment due toabsence of melanin.(can be caused fromsunburn)
Erythema-redness
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What is melanin and where is it found?
What 3 UV rays do we have in our
atmosphere?
What is M.E.D?How long is the average M.E.D?
What are the 2 types of sunscreens?
Name an undesirable effect of UVA and UVB
exposure?
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