The Complexity of Flexity, or, Wing Leery
Purpose:
Although mammalian limbs and bird wings perform different functions, their underlying
anatomy, particularly with regard to joint function and muscle pairing, is similar. The
upper arms of humans, which extend from the shoulder to the elbow, contain a single long
bone, the humerus. The forearm, which connects the elbow to the wrist, contains two
smaller bones, the radius and the ulna. The joints at the shoulder, elbow, and hand, are
composed of bone, skeletal muscle, and connective tissue. Muscles also need neurons and
blood vessels.
Bird wings are likewise composed of an upper wing portion containing a humerus bone
and a lower wing portion containing a radius and ulna, as well as similarly arranged pairs
of skeletal muscles and associated connective tissue.
In this activity we will dissect chicken wings and investigate how muscles, bones, and
connective tissues work together to allow motion. Careful dissection will also allow us to
find some of the nerves and blood vessels that also contribute to joint function.
Procedures:
1. Before you get the chicken, examine the function of a human upper arm. Use one
hand to slowly lift and lower an object. Use the other hand to feel what happens to
your bicep and tricep muscles.
2. Examine the lower arm. Extend an arm and twist your hand as though you are
turning a doorknob. Feel what happens to the radius, which is on the same side as
your thumb, and the ulna. Which one moves, which one is stationary?
3. Get a chicken wing. Rinse it with cool water and dry it off by blotting it with a towel.
4. Examine the wing carefully. Identify the upper wing, the lower wing, and the
wingtip.
5. Examine the shoulder joint, and try to find cartilage, compact bone, spongy bone, and
bone marrow.
6. Cut the skin of the upper wing, from the elbow to the shoulder. Be careful to avoid
damaging the muscles and the connective tissue (fascia) that covers them. Cut down
the side to make a “T” shaped cut. Peel and loosen the skin to remove it. Keep in mind
that surgeons need patience.
7. Observe the clumps of yellow tissue under the skin. What are they?
8. Find the opposing pair of muscles in the upper wing. Hold the shoulder, pull on each
of the muscles and observe what happens.
9. Hold the elbow and do the same thing with the lower wing.
10. Peel back the fascia.
11. Locate some tendons. Pull on them and observe what happens.
12. Locate some ligaments. Figure out what they do. You may have to tease away at the
muscles.
13. Carefully dismantle the joint and find the cartilage.
14. Carefully tease the muscles apart and find blood vessels and nerves.
Observations:
1. Make a neat, labeled drawing (or drawings, if you can’t capture everything in one
drawing) showing the muscle pairs, bone, connective tissue (fascia, tendons,
ligaments, cartilage), nerves and blood vessels.
2. Describe the appearance and function of each of the following tissues: skin, fat,
fascia, muscles, bones, tendons, ligaments, cartilage, blood vessels, nerves.
3. Explain how the structure of cartilage is related to its function.
Bonus:
Explain how the arrangement of muscles and bones in the elbow and shoulder joints of
birds enable different types of movement, and how this enables them to fly.