hands

[jamwan55]

why is it that humans don't have pigment in the palms of their hands

[Clanad]

Well... mine are the same color as the rest of my hands. All humans, excepting true albinos have pigmentation throughout their bodies... it may vary in tint or perceived color intensity due, primarily to the effects of the sun on the melanin contained within the layers of skin...

[don1]

I'm white british and as far as I can see my skin color is fairly equal, my friend dave is a black man and I dont mean he is a bit sunburnt he is as black as the fire back as my grannie used to say, we have been friends since he came to live in Lancashire from the West Indies in 1962

when you shake his hand you know you are shaking the hand of a gentleman, so the back of his hand is black and the palm of his hand is white, so ******* what?

[theprof]

As you probably know, human skin consists of two main layers. The upper layer is called the epidermis, while the lower layer is known as the dermis.

The bottom layer of the epidermis, known as the stratum basale, contains specialised, distorted cells called melanocytes. These melanocytes produce a dark brown or black polymer pigment derived from tyrosine called melanin which is responsible for the overall "darkness" of the skin. The purpose of melanin is to try to prevent harmful UV radiation from reaching the more sensitive dermis. The stratum basale is constantly renewed and the melanocytes and melanin move upwards towards the outermost layer of the epidermis resulting in a fairly even level of pigmentation.

Melanin production is governed by the amount of sunlight that falls on a given skin area. In other words, the more exposed the skin, the darker it becomes in order to protect the skin from UV radiation.

The epidermis has four other layers that sit above the stratum basale before the surface of the skin is reached, so a fair amount of exposure to sunlight or UV radiation is needed before skin browns or even tans.

Contrary to popular belief, different races do not differ in the number of melanocytes in the skin. The only thing that does change is the rate of production and quantity of melanin produced from these cells due to exposure to UV radiation.

The palms of the hands, soles of the feet and a few other areas of the body are normally less exposed to UV radiation than other areas of the body. Therefore, melanin is not needed and the skin in these areas is generally lighter in colour. In addition, these areas contain another thick epidermal layer called the stratum lucidum which gives additional protection.

[Cookaburra]

Just don't need it, that's all

[chamois]

Very enlightening Cookaburra. Can we assume you've not been asked this question in an exam lately?

Thank goodness we've got people like Clanad and theprof on here who can provide a proper rational scientific explanation for this.

It's a bit more than "that's all" after all, isn't it?

[spudmuffa]

Difficult one this. When we are in the uterus and getting our respective pigmentations, our little hands are clasped. Therefore, not allowing pigmentation on the inside of our hands i.e. our palms. You may well ask, why does the foetus clasp its hands? The answer is again quite simple. The foetus is praying to God, that they don't turn out to be a Chelsea supporter. Hope this helps.