Laurel trims superficial fascia/fat.
"Dissecting" a chicken knee picked up from a local butcher, is an excellent way to get to know the tissues of the musculoskeletal system. On September 14, 2011 I led the Drawing Workshop I class at the Center For Cartoon Studies in the exploration of comparative chicken/human/food anatomy.
WHY IS THIS A GOOD IDEA?
Ian examines the cartilage covering the femoral head.
I find this class an excellent way to engage students in the study of the body via a medium they are already familiar with. Students often already have experience of the musculoskeletal system from eating meat. Most of them also understand that the components of the animals they consume are very similar to our own structures.
Disassembling a chicken part by hand give them an understanding of the dimensional aspects of the body, and allows them to relate and compare their parts to animal parts. When presenting this class at the beginning of the term, visual and tactile experience of muscle, tendon ligament, cartilage, etc. gives more significance to lectures later in the semester. Introducing this exercise later in the term provides opportunity for students to recognize the structures and integration of tissues described in previous lectures. In the later classes students often express satisfaction that the body is organized as described in books, and are already familiar with the tissues examined.
Calling this class a "dissection" is pushing the envelope a bit. We are taking the chicken apart in an organized fashion, but the procedure is rather casual. The routine will stay the same from class to class, but the instructional language can vary depending on the focus of the class.
EQUIPMENT
Dan, Mitra, and Ian are ready to go!
ESSENTIAL EQUIPMENT:Plastic sheeting or drop cloths for all working surfaces; plastic bags and buckets for throwing out scraps; latex, vinyl, or nitrile gloves; sharp scissors (dissection, haircutting, etc. Medium or small sizes are best); paper towels and cleaning spray. Chicken thighs contain the femur, knee, and tibia. (They are available at the butchers' or a grocery store.) Clean re-usable equipment in hot soapy water immediately after class.
ADDITIONAL EQUIPMENT: You can buy cheap home-school dissection kits that come with scissors, a scalpel, a probe, etc. I do NOT recommend using scalpels with large groups. Paper plates for holding parts are a nice touch but not necessary as long as you have plastic sheeting on your work surface.
HANDOUTS AND READING ASSIGNMENTS explaining anatomy should be given to students before or at the beginning of class. Encourage them not to take notes during the exercise.
THE CENTER FOR CARTOON STUDIES
CCS first year students.
Thanks to Jon Chad for his photography. Thanks to my most excellent co-teacher, Steve Bissette, for procuring the chicken knees. Steve bought a knee for each student. With large classes (such as this) you can also have them work in groups of two or three.
Mike S, Cole (the hungry one), Luke, and Ian get down to work.
RULES FOR THE EXERCISE
- Never cut the chicken if someone else is holding it for you.
- Always cut away from your hand.
- Cut off (chicken) parts should go in the scrap bucket (almost) immediately.
- Use your hands to disassemble the chicken as much as possible. You can learn a lot by feeling the tissues.
- Try using the scissors to spread tissue apart, instead of always cutting it.
GET ORIENTED
Part of the comparative anatomy lecture.
I am contrasting the organization and use of human toes and avian toes.
We picked up the chicken, grasped the thigh and the shin, and flexed and extended the knee. We located the lateral (outer) skin-covered surface of the leg, then turned the thigh over to see the medial (inner) surface. On this side it's easy to see the head of the femur, covered with hyaline cartilage.
We could also see the muscles of the inner thigh, covered in layers of fascia (connective tissue) with little pockets of fat scattered around. Everyone tried to find a vein or artery with a little blood left in it. We used probes or scissors to push the blood through the tubing.
Skin connects to deeper tissues via superficial fascia. This fascia contains a lot of fat cells, suspended in the collagen fibers that anchor to the skin and deep fascia, below. We peeled the skin off our chickens with our fingers. Sometimes students would feel harder "threads" tear away. These were probably arteries, veins, nerves, or particularly tight bands of fascia breaking.
Once the skin was removed, we could see the shiny, whitish coating of deep fascia covering the chicken's muscle.
At this point, I describe the way muscle cells are wrapped into bundles, which in turn are wrapped into muscles. (The language I use to describe these fascial wrappers varies, depending on the context of the class.)
Then we looked at a muscle's tendon, which is essentially a continuation of the muscle's fascia without any muscle cells in it. Looking at the calf of the chicken, we saw how the Achilles tendon anchors into the muscle. With some creative cutting, we looked at the different shapes and lengths of tendons around the knee, and those working the foot/ankle. We also pulled on tendons to watch the knee move, and/or moved the knee to watch the tendons follow the movement.
(Often this is the place at which we have discussions about muscle fiber pennation, contraction, and the differences between tendon and ligament.)
We trimmed off the quadriceps tendon at the top of the patella (knee cap) and watched it travel between the femoral condyles during flexion and extension of the knee. Then we exposed the medial and lateral collateral ligaments at the sides of the joint. Once we had a good view of the ligaments, we could watch the medial and lateral menisci squish forward and backward between the femur and tibia as the knee was extended and flexed.
Peeling the patella back, we looked at the hyaline cartilage covering its inner surface and the femoral condyles. Flexing the knee as far as it would go and pulling the patella further revealed the knee's deeper fat pads, the cruciate ligaments, and the menisci.
Everyone tried to give their knee a third degree sprain, tearing the ligaments completely. Trying to "break" a knee lets you experience how tough those ligaments are. A couple students' knee ligaments were so strong that the cartilage ripped off the underlying bone while the ligaments stayed intact. For others, the shaft of the bone broke. This was our opportunity to look at the structure of cancellous bone and talk about bone marrow.
I always enjoy these classes. When working our way through the knee, classes typically discuss tissue function and structure, muscle layering, musculoskeletal pathologies such as arthritis and sprain, the difference between stretching and strengthening muscle, and how chicken anatomy compares to human anatomy. There is often speculation as to how people might taste.
A great shot of hyaline cartilage covering the end of a bone, post dissection exercise.
We could also see the muscles of the inner thigh, covered in layers of fascia (connective tissue) with little pockets of fat scattered around. Everyone tried to find a vein or artery with a little blood left in it. We used probes or scissors to push the blood through the tubing.
I used a probe and the school's really cool overhead projector to show
the students what a vien (or artery) looks like.
(I couldn't tell what type of vascular structure it was - it's a chicken, for cryin' out loud!)
SKIN
Sophie at work pulling the skin off her chicken.
Skin connects to deeper tissues via superficial fascia. This fascia contains a lot of fat cells, suspended in the collagen fibers that anchor to the skin and deep fascia, below. We peeled the skin off our chickens with our fingers. Sometimes students would feel harder "threads" tear away. These were probably arteries, veins, nerves, or particularly tight bands of fascia breaking.
Trimming through some stubborn skin at the chicken's ankle.
DEEP FASCIA, MUSCLE, AND TENDON
Sasha, Laurel, and Rachel examine deeper tissues.
Once the skin was removed, we could see the shiny, whitish coating of deep fascia covering the chicken's muscle.
At this point, I describe the way muscle cells are wrapped into bundles, which in turn are wrapped into muscles. (The language I use to describe these fascial wrappers varies, depending on the context of the class.)
Deep fascia is exposed once the skin is removed.
Then we looked at a muscle's tendon, which is essentially a continuation of the muscle's fascia without any muscle cells in it. Looking at the calf of the chicken, we saw how the Achilles tendon anchors into the muscle. With some creative cutting, we looked at the different shapes and lengths of tendons around the knee, and those working the foot/ankle. We also pulled on tendons to watch the knee move, and/or moved the knee to watch the tendons follow the movement.
(Often this is the place at which we have discussions about muscle fiber pennation, contraction, and the differences between tendon and ligament.)
Someone has made a portrait from skin and muscle
resembling Inky Solomon, CCS's mythical mascot and founder.
The fascia in the "beard" gives it a wispy appearance.
DECONSTRUCTING THE KNEE JOINT
Luke has trimmed all the superficial tissues away, exposing the knee joint.
We trimmed off the quadriceps tendon at the top of the patella (knee cap) and watched it travel between the femoral condyles during flexion and extension of the knee. Then we exposed the medial and lateral collateral ligaments at the sides of the joint. Once we had a good view of the ligaments, we could watch the medial and lateral menisci squish forward and backward between the femur and tibia as the knee was extended and flexed.
Peeling the patella back, we looked at the hyaline cartilage covering its inner surface and the femoral condyles. Flexing the knee as far as it would go and pulling the patella further revealed the knee's deeper fat pads, the cruciate ligaments, and the menisci.
Mike C flexes the knee and holds back the patella with his thumb.
Everyone tried to give their knee a third degree sprain, tearing the ligaments completely. Trying to "break" a knee lets you experience how tough those ligaments are. A couple students' knee ligaments were so strong that the cartilage ripped off the underlying bone while the ligaments stayed intact. For others, the shaft of the bone broke. This was our opportunity to look at the structure of cancellous bone and talk about bone marrow.
IT'S A CONVERSATION STARTER
My wonderful teaching assistant, Rio, helps me compare human and chicken knee flexion.
I always enjoy these classes. When working our way through the knee, classes typically discuss tissue function and structure, muscle layering, musculoskeletal pathologies such as arthritis and sprain, the difference between stretching and strengthening muscle, and how chicken anatomy compares to human anatomy. There is often speculation as to how people might taste.
MORE IMAGES FROM THE EXERCISE
Romey uses a probe while Mike C is flexing the knee.
Life drawing teacher, Bill Scavone, has exposed nerves and vascular structures.
(They are easiest to see in the top third of the image.)
The overhead projector was a life-saver with such a large class.
