everyones skin contains about the same amount of melanocytes even though people are many different colors.how?

Question

Everyones skin contains about the same amount of melanocytes even though people are of many different colors. How is this possible? This was asked in my A&P class today, and we were all floored!
any ideas anyone?
I need an actual scientific answer, not opinions!!
Thanks all!!!

Answer 1

Melanocytes are cells located in the bottom layer of the skin's epidermis and in the middle layer of the eye, the uvea. Through a process called melanogenesis, these cells produce melanin, a pigment in the skin, eyes, and hair. There are both basal and activated levels of melanogenesis; lighter-skinned people generally have low basal levels of melanogenesis, and exposure to UV radiation generally causes increased melanogenesis.

There are typically between 1000 and 2000 melanocytes per square millimeter of skin. They comprise from 5% to 10% of the cells in the basal layer of epidermis. Although their size can vary, melanocytes are typically 7 micrometers in length. The difference in skin color between fair people and dark people is due not to the number of melanocytes in their skin, but to the melanocytes' level of activity.

Answer 2

Think of it this way: everyone also has the same number of legs (more or less), but some people walk a lot further than others.

Melanocytes respond to both genetics and environment. Genetically, some people have instructions that tell their melanocytes to produce a lot of melanin, so they look darker than other people. Environmentally, some people spend more time in the sun than others, so their melanocytes respond by producing more melanin as a defense and these people consequently look darker than others.

To complicate the issue, there are several different variants of melanin pigments, and many people express more than one of them. These are genetically controlled as well.

Hope that helps!

Answer 3

Melanocytes are just speacialized cells that produce a chemical called melanin. Melanin is what determines skin pigment and color, not the number of melanocytes. So its not what you have, but what they are genetically instructed to produce.

Answer 4

Everyone has the same number of melanocytes, but everyone's level of melanogenesis (when those cells produce melanin) is not the same.

Fair people have low levels of melanogenesis. Exposure to sun increases melanogenesis, which explains how sunbathing darkens the skin tone.

Answer 5

We also have the same number of hair pores per sqare inch as a gorilla, to take another example. It's a question of gene expression. The structure is there (melanocytes, hair pores) but how will it develop? Depends on the gene expression as well as the genes themselves.

;-)