Module 8: A
Diversity of Skin Types
Objective: Learn how
skin color plays a role in sun protection and vitamin D activation.
Think about all the
different skin colors in the world. Look around your classroom. You'll
find a small sample of the many natural skin shades that make humankind
wonderfully diverse. What causes differences in skin color? And how does
skin of different types respond to ultraviolet (UV) rays? Why is it
important to know your skin type? This module will help you answer these
questions.
A
Review of Melanin and Melanocytes
As you learned in module
1, "The Skin":
- Melanin is the
pigment that colors the skin.
- Skin color depends
on how much melanin is made and carried to the upper layers of the
skin. The more melanin in the upper layers, the darker the skin.
- Melanocytes are the
cells that make melanin. They are in the basal layer of the epidermis.
- All people basically
have the same number of melanocytes, no matter what their skin color.
- Tanning happens when
UV rays cause more melanin to be made and carried to the upper layers
of the skin.
Melanin is important in
keeping us and our skin healthy. Melanin protects a cell's genetic
material from ultraviolet damage by forming a cap over the nucleus. The
cap can directly absorb harmful UV rays. Melanin can also
"scavenge," or clean up, toxins that result from ultraviolet
damage to skin cells. So melanin plays a very important role in preventing
skin damage and even cancer in a sunny environment.
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Skin
Color and Vitamin D
There is another
important factor at play when it comes to skin color: vitamin D. UV rays
"activate" vitamin D in the skin. Our bodies need vitamin D to
absorb calcium for building strong bones and teeth. People who don't get
enough vitamin D risk bone problems. These problems include weak bones and
diseases such as rickets and osteomalacia. Rickets can lead to bent or
distorted bones. Osteomalacia is softening of bones.
Lighter skin lets in
more UV rays than dark skin. So lighter skin makes the most of whatever
sunlight there is for activating vitamin D. This makes sense when you look
at how skin color is distributed around the world. People originally from
cold, dark climates tend to have lighter skin than those from sunnier
regions.
For more information on
vitamin D, check out
http://ods.od.nih.gov/factsheets/vitamind.asp.
Today, people with
different skin types live all over the globe. They live in environments
with all different levels of ultraviolet radiation. Too little vitamin D
is not a common problem for people who eat healthy, varied diets.
But skin cancer and skin aging are common. Knowing your skin type
can help you choose the best ways to protect your skin from the sun. See module
9, "Know Your Skin Type."
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