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Guided Inquiry • Skills Lab
Chapter 32 Lab Comparing
Limbs
Problem
How is the structure of skeletal muscles and bones related to the functions of these
body parts?
Introduction
Although humans sometimes use all four limbs to move around, most of the time
humans use their legs and arms for distinctly different functions. Legs support the
body and carry it from place to place, while arms lift and carry objects.
Despite these differences in tasks, arms and legs have similar overall structures.
The upper part of each limb is supported by a single bone, and the lower part of each
limb is supported by two bones. Pairs of opposing muscles move the bones around
their respective joints.
Do the limbs of other vertebrates have similar arrangements of bones and
muscles? For example, is the wing of a bird similar to a human arm? In this lab, you
will begin by comparing the motion of arms and legs. Then, you will dissect a
chicken wing and compare its internal structure to that of a human arm.
Skills Focus
Observe, Infer, Compare and Contrast
Materials
• disposable plastic
gloves
• chicken wing
• disposable dissection
tray
• dissecting scissors
• forceps
• colored pencils or markers
Safety
Disease-causing species of Salmonella bacteria may be present on raw chicken. To
avoid infection, wear gloves and avoid touching your eyes, nose, and mouth. Use the
dissecting scissors only as instructed to avoid injuring yourself and others. Dispose of
materials only as instructed by your teacher. Wash your hands thoroughly with soap
and warm water before leaving the lab.
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Pre-Lab Questions
1. Observe How will you observe the structure and function of your elbow
and knee joints?
2. Relate Cause and Effect Why is it important to wear goggles and
disposable gloves while examining the chicken wing?
3. Predict Will the arrangement of bones and muscles in a chicken wing be
similar to the arrangement in a human arm? Why or why not?
Procedure
Part A: Observe the Motion of Human Limbs
1. Extend your right arm with the palm facing down and place two fingers of
your left hand on the tip of your right elbow. Bend your right arm and then
straighten it out. Describe any movement at the tip of your elbow.
2. Extend your right arm with the palm facing down and place two fingers of
your left hand on the tip of your right elbow. Keep your arm straight while
you rotate your hand so that your palm faces up, and then rotate your hand
back to its original position. Describe any movement at the tip of your
elbow.
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3. Keep your right arm extended with the palm facing down. Place the fingers of
your left hand under your right forearm just above the wrist. Rotate your hand so
that your palm faces up, and then rotate your hand back to its original position.
Describe what you feel.
4. Sit in a chair with your feet flat on the floor. Place the fingertips of your right
hand on the middle of your kneecap. Raise your lower leg. Describe what
happens to your kneecap.
5. Raise your lower leg again. Try to turn your foot so that the sole of the foot is
facing up. Describe what happens.
6. Look at the drawings in Figure 1. Identify the muscles that bend and straighten
the elbow and knee joints.
Figure 1 Muscles in a human arm and leg
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Part B: Observe the Structure of a Chicken Wing
7. Put on goggles and gloves. Place a chicken wing in the dissecting tray and
observe its structure. On the drawing in Figure 2, label the upper wing,
lower wing, joints, and wing tip.
Figure 2 External Anatomy of a Chicken Wing
8. Bend and straighten the joint between the upper wing and the lower wing.
Bend the joint between the lower wing and the wing tip. Describe the
motion you observe.
9. You will next cut the skin of the upper wing from the shoulder to the first
joint. To start the cut, slide the tip of one blade under the skin at the
shoulder. Lift up the skin as you cut to avoid damaging the tissues beneath
the skin. Make a second cut on the opposite side of the wing. CAUTION:
Handle the scissors carefully to avoid injuring yourself or others.
10. Use your fingers to peel away the skin from the upper wing. To completely
remove the skin, you will need to carefully cut the bits of connective tissue
that attach the skin to the muscles.
11. Repeat Steps 9 and 10 to remove the skin from the lower wing.
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12. After you remove the skin, use the forceps or your fingers to gently separate the
muscles from one another. Use the space below to make a sketch that shows the
muscles.
13. Pull on each muscle, one at a time, to see whether the muscle bends or straightens
a joint. Identify the opposing pairs of muscles and color-code these pairs on your
drawing.
14. Trace each muscle to the joint between the upper and lower wing. Cut the shiny
white tendons that connect the muscles to the joint and peel back the muscles. In
the space below, sketch the arrangement of the bones around the joint.
15. Follow your teacher’s instructions for disposal of the chicken wings, dissecting
trays, gloves, and paper towels. Wash the scissors and forceps and any surfaces
you might have touched while doing the dissection. When you are done, wash
your hands thoroughly with soap and warm water.
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Analyze and Conclude
1. Compare and Contrast How was the motion at your elbow joint similar
to the motion at your knee joint? How was it different?
2. Infer How is the ability to rotate the bones in the forearm an advantage for
humans?
3. Infer How is it an advantage for the human knee to have a smaller range of
motion than the human elbow?
4. Observe In the chicken wing, where were the muscles that bend and
straighten the joint between the upper and lower wing located?
5. Compare and Contrast Identify structures in the chicken wing that are
homologous to bones and joints in the human arm. Use Figure 32–1 in your
textbook, Figure 1 in this lab, and your observations of the chicken wing.
Extend Your Inquiry
View prepared slides of skeletal muscle and bone. Draw a sketch for each type
of tissue. Then, write a paragraph explaining how the structure of each type of
tissue is adapted to its function.
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