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Global Atmospheric Change

Author(s): Nancy Moreno, Barbara Tharp and Judith Dresden

Measuring and Protecting Skin

Skin protects inner tissues of the body and provides communication (through the sensory system) with the outside world. The skin also helps maintain a constant temperature within the body by aiding in cooling (through increased blood flow to the surface and perspiration) and heating (by reducing blood flow near the surface).

The skin is comprised of different layers. The outermost layer, the epidermis, consists of an inner layer of living cells and a top layer of compacted dead cells. In fact, most skin that is visible on our bodies actually consists of dead cells! Skin color is determined by special cells, called melanocytes, located near the base of the epidermis. The lower layer, the dermis, is fibrous and gives strength to skin. Most nerve receptors that capture information from the outside world are located at the top of the dermis or the base of the epidermis.

Skin can be damaged by ultraviolet (UV) radiation from the sun or tanning lights, which can cause premature wrinkling and loss of elasticity of the skin, as well as skin cancer. Sunburns and suntans both are evidence that skin has been exposed to too much harmful radiation. Due to ozone depletion in the upper atmosphere, more UV radiation is reaching Earth’s surface.

This has increased the risks for damage to skin and eyes (particularly through the development of cataracts).

This activity builds awareness of skin by having students contrast and compare the “skin” of an orange to human skin. Students also will compare the surface area of an orange to the area of a person’s skin.


Skin is especially vulnerable to the effects of ozone depletion in the upper atmosphere. Ultraviolet radiation produced by the sun can damage skin, causing premature wrinkling and loss of elasticity, as well as skin cancer. As increased amounts of UV radiation reach the surface of the planet, the risks for skin damage also increase. Sunburns and suntans both are evidence that skin has been exposed to too much damaging radiation.

Reductions in the amount of ozone in the stratosphere are allowing more ultraviolet radiation (UV) from the sun to reach Earth’s surface. The effects of some kinds of UV exposure are cumulative and may not show up for many years. In humans, increased exposure to UV radiation (especially UV-B, with wavelengths between 290–320 nanometers) is linked to skin cancer, the development of cataracts and effects on the immune system. UV-B radiation also is toxic to plants, including crop plants, and phytoplankton, which forms the basis of marine food chains.

Session 1: Estimating surface area of an orange

  1. Generate student interest by brainstorming about things that have a skin. List student ideas on the board. Older students may record the list in their science notebooks.

  2. Discuss the purposes of skin (tree bark, skin on a banana, lizard skin, bird skin, etc.) based on the list of things with skins.

  3. Holding an orange, explain to students that they will be examining the skin of an orange and comparing it with their own skin. Ask, How is the skin of an orange like your skin? How is it different?

  4. Have Materials Managers collect materials for the groups. Each group will need: an orange, paper towels, plastic knife, tape measure, sheet of writing or notebook paper, and two or more sheets of centimeter square graph paper.

  5. Begin the group activity by having one student (Recorder) list the group’s observations about the skin of the orange. Then place a check next to all observations that also would apply to human skin.

  6. Next, ask, How much skin does an orange have? How could we find out? Instruct students to estimate the amount of skin on their oranges by coloring a similar area on their graph sheets. They may want to measure their oranges using tape measures. With older students, use this opportunity to investigate the relationships among diameter, circumference and area.

  7. Ask, How could you check your estimates? Have students peel the oranges and, within each group, trace the peelings onto graph paper. Have them color the traced areas orange. Have students calculate the area that is colored by counting or measuring the number of squares filled in, and decide how much skin their oranges really have. Let students devise their own methods for counting partially colored squares, or instruct them to count every other partial square. Ask, Are you surprised about the area covered by the skin? Why or why not?

  8. Next, have the students examine the peeled oranges. Discuss what might happen if oranges didn’t have skin.

Session 2: Estimating the amount of skin on a person

  1. Explain that, just like oranges, our bodies need protection. Mention some of the characteristics of skin: it is the body’s largest organ; skin provides protection from germs; it houses our cooling and heating systems; skin contains receptors for our sense of touch, etc. Refer students to the diagram of skin on page 8 of the Explorations magazine.

  2. Ask, How much skin do you have and how do you protect it? Students can record their estimates in cm2 in their science notebooks and list ways they protect their skin.

  3. Tell students that the area of skin on the body can be measured with relative accuracy by applying the Law of Nines. This rule of thumb was developed to help doctors estimate the amount of skin damaged on people with burns. Roughly, each of the 11 major sections of skin on the body accounts for 9% (or 1/11) of the total (see illustration, right). Using this rule, students can estimate the total surface area of skin on their bodies by measuring the area of one arm.

  4. Working in teams of two, have one student wrap another’s arm in wax paper. Have them mark any areas of overlap, so that they will not be counted for the estimate of surface area.

  5. Have them spread the paper out over two or more sheets of centimeter graph paper and count the number of squares covered (or have older students measure the dimensions of the wax paper and calculate the area as if it were a rectangle, or a rectangle and one or more triangles, showing area calculations).

  6. Once students have found the surface area of an arm, have them multiply that figure by 11 to obtain the total surface area of skin on the entire body.

  7. Ask students to imagine how they might look and feel without their skin—just like the peeled orange. Mention the importance of protecting skin from damaging UV radiation. Discuss strategies for protecting skin, including wearing clothes with long sleeves, always applying sunscreen, wearing hats, etc.

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education