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Skin Anatomy Lab

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					Name:______________________________


                        Skin Anatomy & Physiology
       The following three experiments will have you investigate the anatomy of the skin and
some of its physiology. Each group member will need a hand lens. Each group will need a black
and red felt marker, a metric ruler, a calculator, and four pennies. These supplies should all be
returned to the baggie when the lab is finished.

Anatomy of the skin: First, using a hand lens, each lab group member should examine the skin
on the back of the hand. Note the furrows and ridges. Trace some of the blood vessels lying
under the skin. Try to lift the skin. Examine the skin on the palm of the hand. Note the furrows,
ridges and creases. Look for moisture and calloused areas. Compare the thickness of the skin
here with the skin on the back of your hand. Try to lift the skin of your palm. Record your
observations. For the second data table, observe your teacher’s hand using the ProScope digital
microscope.

                                            Anatomy
   Skin Area                              Observations about appearance:

Back of hand


Palm of hand



                              Anatomy of hand under the ProScope

   Skin Area                   Observations about appearance: (draw a sketch too!)
Back of hand:

50x

Back of hand:

50x

Palm of hand:

100x

Palm of hand:

100x
                                             Physiology Part 1

Physiology Experiment #1: Tactile localization is the ability to determine which portion of the skin has
been touched. Certain body areas are well represented with touch receptors, and stimuli can be localized
with great accuracy, but other areas do not have many receptors which only allows for crude
discrimination.

The subject’s eyes should be closed during the testing. The experimenter touches the palm of the subject’s
hand with a pointed black felt-tipped marker. The subject should then try to touch the exact point with his
or her own red felt-tipped markers. The “error of localization” is the measure of the distance between
your initial mark and their attempted mark. Measure the error of localization in millimeters. Repeat the
test in the same spot twice more, record and then calculate the average and record. Repeat the experiment
on the fingertip, back of the hand, and ventral forearm and record your results.


Tactile body           Error of               Error of               Error of               Average error of
testing area           localization           localization           localization           localization (mm)
                       reading #1 (mm)        reading #2 (mm)        reading #3 (mm)


Palm of hand

Fingertip

Back of hand

Ventral forearm

                                             Physiology Part 2

Physiology Experiment #2 - The second experiment will demonstrate that in many cases, when a stimulus
is applied for a prolonged period, the rate of receptor response slows and conscious awareness of the
stimulus declines or is lost until some type of stimulus change occurs. This phenomenon is called
adaptation. The touch receptors adapt particularly rapidly which is highly desirable because why would
we want to be continually aware of the pressure of clothing on our skin?

The subject’s eyes should be closed. Place a coin on the anterior surface of the subject’s forearm and
determine how long the sensation persists for the subject. Record the time. Repeat the test, placing the
coin at a different location and determine how long the sensation persists and record. After the awareness
of the sensation has been lost at the second site, stack three more pennies atop the first one. If the pressure
sensation returns, determine how long the subject is aware of the pressure in this instance and record.




Touch adaptation time – site #1                                                             seconds

Touch adaptation time – site #2                                                             seconds

Pressure adaptation time – site #2                                                          seconds
                                            Physiology Part 3

Physiology Experiment #3: There are different types of nerve receptors in the skin. Some receptors detect
pressure. Others detect heat, cold and pain. If a student pushes the pencil point near a "cold" receptor, the
point feels cool. At another site the point feels much sharper but not cold.

In some areas of the skin, there is much space between the receptors. In other areas, such as skin over the
lips, the receptors are bunched close together. That is why lips are very sensitive. Think about the
different areas of your skin and which areas may be more or less sensitive than others.

In this experiment, choose two of the four possible skin areas to use. Your options are: back of your
hand, your palm, your ankle area, or your forearm. You will test your two areas for receptor sensitivity.
Have your partner mark off one square-inch area in each of your two testing sites. Predict which area will
have the most of each kind of receptor.

Hypothesis (if, then format!!):
_____________________________________________________________________________________
_____________________________________________________________________________________

Use the end of a toothpick or bamboo skewer to gently poke the skin at any point within the one inch
square boundary, being sure not to break the skin. Take careful note of the sensation as your skin is
being tested. Move the point of the pencil one or two millimeters in any direction and push again. Make
note of the sensation. At some sites within the square inch students will detect a cold feeling. At other
sites the pencil point will feel hot, pointed and painful, or there will be no sensation at all. Record your
data in the table provided (use tally marks). You should test at least ten different areas within each
square. Perform the activity again on the other square. Compare it to your predictions.

     Skin Area Being
                                      Cold?                     Hot?                 No Feeling?
         Tested

    _________________



    _________________



Discussion Questions:

    1. What surprised you about the way human skin looks when it is magnified fifty or one
       hundred times?




    2. What would be an advantage to the way the skin is attached to the palm of the hand
       instead of how the skin is attached to the back of the hand?
3. What is tactile localization?




4. During the tactile experiment, does the ability to localize the stimulus improve with each
   time the experiment is done? Explain.




5. During the tactile experiment, which area has the smallest error of localization (is the
   most sensitive to touch)? Why do you think that is?




6. After the adaptation experiment, would you say that the same receptors being stimulated
   with the four coins are the same receptors stimulated with the one coin?




7. What areas of your skin are more sensitive to hot/cold stimuli?




8. Why is it beneficial to humans to have sensory receptors more heavily distributed in
   certain areas of the body, instead of every location being equally sensitive?

				
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posted:11/8/2011
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