First Line of Defense: Skin
Careful observation is one way to learn about the skin.
Look at your own skin. Describe it. How many words can you come up with
to describe the surface of your skin?
Diagram of a block of skin
and Studying Skin
You can't really see how skin acts as a barrier by only superficial observation.
To look closer, we need to examine skin under a microscope. To do this,
you need a piece of skin (from a dead animal for example) and you need
to complete a series of steps that make the cells visible under a microscope.
This process will be examined more thoroughly as you complete the activities
for this unit, but roughly, the steps to examine skin under a microscope
The skin sample has to be sliced very thin,
so that the sample
is translucent (light can be seen through it).
2. Place the skin sample on a microscope slide.
3. Stain the slide so that cell parts become visible.
Once these steps are completed, you will be able to view
the skin cells, as shown in the photo on the right. You can also create
a slide of cells by gently scraping the inside of your cheek with a
toothpick and rubbing the toothpick on a slide.
To learn about the chemical properties of skin, you can put various substances
on the outer surface and observe what happens. Some substances just stay
on the surface, while other substances disappear (dissolve) into the skin.
Can you think of some substances that are absorbed into the skin?
What are some other conditions or situations that
can impact your skin?
What happens when infection gets beneath the skin and
breaks through the first line of defense? Your body relies on its second
line of defense - the immune system.