HUMAN SKIN
- its color

• wide variety of skin colors
  • skin color varies widely across the globe:
    • between different ethnic/racial groups
    • between individuals within the same ethnic/racial group
• what determines skin color ?  - skin color is determined by the interaction of a variety of factors:
  • skin thickness -
    • different areas of the body have different thicknesses of skin
      • e.g. - the skin of the lips is very thin, blood flow is abundant, thus they are more red in color because of the haemoglobin pigment present in blood 
  • blood flow -
    • the richer the blood flow and the closer the blood vessels are to the surface of the skin, the more pink or red the skin will appear
  • pigment concentration - 
    • the production of the pigment melanin, produced by the melanocyte cells found in the epidermis, determines the darkness of the skin 
  • genetics / ethnicity -
    • people who can be traced their ethnicity to more tropical or sun rich areas have genetically higher concentrations of melanocyte cells, subsequently they produce more of the pigment melanin 
  • sun exposure -
    • when exposed to sun, the melanocyte cells respond in a defensive manner, by producing more melanin to protect the skin against ultraviolet (UV) rays
    • as the amount of UV exposure increases, more melanin is produced, resulting in a proportional darkening of the skin's color
    • freckles, dense clusters of melanocyte cells, are another way the skin responds to UV exposure
  • people with a condition know as albimism (albinos), have very few to no melanocyte cells, and thus appear very pale skinned

The map below provides a good overview of the distribution of skin color across the world: