Chicken Wing Dissection
Teacher Notes by Jim Ekstrom
The chicken wing dissection is a great introduction to animal anatomy and physiology. It gives students an overview of the various tissues and systems they will be studying in the weeks ahead in Human Anatomy/Physiology.
I purchase chicken wings at the market the day before using them. By doing this, and having students follow precautions during the exercise, there should be little or no chance of salmonella infection. If you are working with "other than fresh birds" you may want to soak them for several hours in 70% alcohol prior to dissection. I find the alcohol treatment somewhat reduces the natural contrast between tissues that you get with "fresh birds."
I have students work in pairs. There are several reasons for this; one of which is to reduce skin-removing fatigue. The toughest thing about the chicken wing dissection is the time-consuming skin removal. I generally allow about 20 minutes for this process and during this time I have the students make the following observations.
About the chicken wing image:
The picture, by the way, was taken with a Macintosh QuickTake camera of a student chicken wing dissection. I use this picture to show an "average" student quality dissection. I make a number of color transparencies using special transparency film and a $300 color laserjet printer.
Depending on how much time you have to linger over details--or how much skin you want to remove--this lab exercise takes from 50 to 75 minutes to complete.
I would appreciate any additional suggestions/comments from people who have done this dissection. Jim Ekstrom.
- When the wings are removed the "butcher" may have made a clean slice and neatly severed the upper wing bone from the body socket. If this is the case you can see the shiny cartilage covering the end of the upper wing bone. If the cut is sliced into the bone you can see the spongy bone tissue. If the cut is even deeper you will see the bone marrow similar to what is showing in the lab exercise picture.
- If you have the first scenario with the whole end of bone showing you might want to talk about the role of articular cartilage (hyaline cartilage) in joint movement and the fluid that assists this movement. (In Intro Biology we just use the term cartilage.)
- If the spongy zone of the bone is showing, you may want to talk about this network of bone strengthening struts and the effect of osteoporosis on this area.
- If the bone marrow is showing then you have one of the sites of red blood cell production (Label 1 in Figure 2). I generally have students move around from tray to tray to see these different views.
- The most efficient way to remove the skin is to start at the top (proximal) end of the upper wing with your scissors. Keep the point of the scissors up as you cut down the middle on either the ventral or dorsal side. Cut down to a joint and then trim to either side of your cut. When you do this you are cutting below the dermis and above the muscle. The dermis is largely composed of loose connective tissue that ordinarily anchors the skin to the muscle layer. (Pinch up your skin on the back of your hand to show this separation as well as the elastic recoil back to the original position.) Adipose tissue (fat) is another form of connective tissue that can be seen adhering to the underside of the skin. It is also apparent that the upper wing has a single bone (like our humerus) and the lower wing has a double bone structure (like our radius and ulna). How this arrangement lends itself to flexibility as well as coordination can be commented upon.
- The muscles are contained within semi-transparent containers of connective tissue. (Labels 2 through 6 on Figure 2 show several muscle groups.) To demonstrate which muscles are extensors and which are flexors it is necessary to loosely hold the wing by the upper wing bone in a horizontal manner. This will make it easy for a student to pull on the muscle with their fingers/forceps and see what part of the wing extends or flexes. Students should be able to find a pair of extensor/flexors in both the upper and lower wings.
- The white tendons connecting muscle and bone can be seen in several upper and lower wing muscle groups. (Label 7 shows one of the most easily seen tendons.) Where these tendons run over joints--like the "elbow"--they are often in well developed sheathes.
- Ligaments are not as easily seen as tendons. It may take a little digging to show these bone to bone connections. (Label 8 on Figure 2 is a good spot to see these specialized connective tissue structures.)
- It is also possible to see blood vessels and nerves between muscle bundles and muscle bundles and bones. It is necessary to do some teasing to see these structures and it is worthwhile to have various student groups share their results at this point.
- Lastly, if the students sever a flexor muscle of a particular pairing it should further confirm the role of the extensor that it was originally paired up with. (Possibly sever a flexor in the upper wing and an extensor in the lower wing.)