Melanocytes,Electromagnetic Spectrum and the Effects of UV On

8/13/2019 Melanocytes,Electromagnetic Spectrum and the Effects of UV On

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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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Melanocytes,Electromagnetic Spectrum and the Effects of UV On