Skin Colour

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I was trying to find an article on pigmentation on big Medical Texts and could not.

This was an extraction from a very old power point presentation.

I have destroyed my notes by conviction.

When we were medical students there were good articles on pigmentation, not now (? new policy).


I am much interested in Guppy and Zebra fish pigmentation not human.


Skin Colour


Skin colour is determined by two factors.

One is the amonut of melanin formed in response to sun's radiation effects.

This amount of formation of melanin is determined by different  alleles and are poly-geneticaly inherited.


There is hardly any difference between whites and blacks in melanin formation.


The second is the packaging of that melanin in membrane bound packs.

White skin people lack the ability to form (melanasome melanisation) membrane bound packages efficiently.

Melanosomes are either degraded or dispersed in white skin.

It is a genetic deficiency and not a superior quality of white man.
White man is deficient and why and when this happened is currently unknown.

That is why they are prone to cancer and a very serious condition, the malignant melanoma.
They cannot sun bathe in reality.
This happened during their migration while dark skinned people retained that ability and were protected from cancer.

Additionally dark skin is resistant to weathering and old age.

Melanins

The are several varieties of melanins

Eumelanin
Dark brown melanin proper
Chemically an insoluble polymer of tyrosine
Phaeomelanin
Yellow or red skinheads
Chemically a polymer of tyrosine and cysteine, soluble in alkali solutions
The are several varieties of melanins
Eumelanin is present in skin, hair, pigment epithelium of the eye, in the meninges, in brain stem (substantia nigra) and adrenal medulla
All these organs are ectodermal in origin like the nervous system
Produced by the melanocytes and are packed membrane bound and are transmitted to surrounding keratinocytes.
Each melanocyte actively implants its granules into the body of the nearby cells.
One melanocyte supplies melanin to thirty-three keratinocytes according to signals from the keratinocytes.
In other words roughly 100 cells of the epidermis have three melanocytes.

Black Skins
In black skin the melanosomes which are larger than those of white skin remain free.

White Skins
In white skin the melanosomes are taken up by the autophagosomes and are degradaed.
They are dispersed lightly causing the social pathology

Light absorption
Functions of Eumelanin is to bsorb ultraviolet and visible light and get oxidized in the process
It is a Free Radical sink, so prevent carcinogenesis.
Black skin ages better than whites
It is an Ion-exchange resin
Melanin is an electron acceptor and binds many drugs Chlorpromazine
Melanins are biologically very important but very little is understood
Their physiochemical properties are frustrating to the chemists
Much remains to be learned
Little fish called Zebra (also Guppy) is unraveling its mysteries
The pathology of melanin is largely a matter of increased or decreased pigmentation
Hypopigmentation
Hyperpigmentation