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This question group is public and is used in 12 tests.

Author: szeiger
No. Questions: 5
Created: Feb 21, 2015
Last Modified: 5 years ago

Why Do Fingers Wrinkle

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When you get out of the bathtub and look at your fingers, you might notice that they look wrinkled. Why do fingers wrinkle in the bathtub?

In the past scientists thought the answer was pretty simple. They explained it as follows: When you sit in the bathtub for a long time, the outer layer of your skin absorbs water. Your skin contains a protein called keratin. This outer layer is made up of dead keratin cells and they start to swell because of all of the water. To stay on your skin, the dead cells are tightly attached to the living layer of skin. When they swell, they start to wrinkle to make room for the extra area of dead cells caused by the swelling.

Your hands and your feet have thick layers of dead keratin cells. No other parts of your body have the same thickness of dead cells. That's why only your fingers and toes wrinkle when you stay in the bath too long.

Today, scientists have new ideas about why your fingers wrinkle. You skin is covered with sebum, which is a special oil. This oil makes it possible for water to just roll off your fingers. However, as you sit in the bathtub, your body starts to lose some of the sebum. As a result, the water sticks to your fingers more.

It's then that your fingers start to wrinkle. Your body's nerves react to the lack of sebum and high amounts of water by starting to wrinkle. Other parts of your body lose sebum too, but only your fingers and toes appear to wrinkle. This is partly because they're smaller and it's easier to notice the wrinkling. It's also because your body thinks it's easier to grasp items with wet fingers when they're all wrinkly. Your body keeps producing sebum even while you're in the bathtub though, so as soon as you get out of the water and your fingers start to try out, they go back to normal.
Grade 3 Nature and Science (Stories) CCSS: CCRA.R.3, RI.3.3
Why is sebum important?
  1. It helps the skin absorb water.
  2. It keeps the fingers from wrinkling.
  3. It causes water to roll off the skin.
  4. It helps skin stay safe in the bathtub.
Grade 3 Nature and Science (Stories) CCSS: CCRA.R.1, RI.3.1
What makes your fingers wrinkle?
  1. The water
  2. The sebum
  3. Your body's nerves
  4. Your body's temperature
Grade 3 Nature and Science (Stories) CCSS: CCRA.R.1, RI.3.1
Grade 3 Nature and Science (Stories) CCSS: CCRA.R.3, RI.3.3
Which reason best explains why your skin goes back to normal when you get out of the tub?
  1. Your nerves tell it to
  2. The water dries up
  3. Your body warms up
  4. The sebum comes back