Krieger Science Blog

A few ideas for home science education projects...

Dissecting A Chicken Leg

Observe the musculature and bone structure in a leg similar to your own.


As I said in my post on dissecting chicken wings, the dissection of higher animals gives us the opportunity to observe and probe internal structures that resemble those in our own bodies. The wing makes a nice analog to the human arm, and the chicken leg makes an equally nice analog to a human leg. In fact, chicken legs are even easier to study than wings, because they are larger, with parts that are easier to examine and work with, and the skin comes off much more easily. A drawback is that the feet aren't normally included, although you can buy those separately, as I mentioned in my post on the workings of the hand.

Supermarkets normally sell "leg quarters", which consist of a thigh and drumstick still united. This is what a leg quarter looks like:

A chicken leg quarter from a grocery store
A Chicken Leg, Fresh from the Package

Just as the pieces of a wing correspond to those in a human arm, the pieces of a chicken leg correspond to those in a human leg. The muscular section closest to the body is the thigh, the middle section (the drumstick) corresponds to the human lower leg, and if the foot were still attached, it would follow the drumstick. As with the wing, we need to remove the skin to discover the muscle structure underneath. Fortunately, the skin comes off of a leg much more easily than from a wing. You don't even need scissors. You can reach inside the hip end with your fingers and pry the skin free from the underlying tissue, then gradually peel the skin inside out off the ankle end, like taking off a sock. You will find only one place where the skin is hard to remove — around the ankle. This is what a skinned leg looks like:

A chicken leg quarter with the skin removed, showing the musculature
A Chicken Leg with the Skin Removed

The biceps and triceps on a chicken wing, like those in a human arm, are single, clearly identifiable muscles. The larger muscles on a chicken thigh do also correspond to the quadriceps and hamstring muscle groups in a human leg, but like the human quadriceps and hamstrings, they are muscle groups, bundles of several inter-grown muscles, and they aren't as easy to identify individually.

From this point on, I don't have a systematic procedure to offer. Think of the rest of the dissection as an exploration, in which you gradually disassemble the leg to see what you can see. I recommend paying special attention to the drumstick. Some of the things I have observed are as follows:

If you've read my post on the hand, you will recall how chicken feet and human hands work like marionettes. Similarly, the human forearm, and the chicken drumstick, are the "puppetmasters", containing an assembly of muscles with drawstrings running through the wrist/ankle out to the hand/foot. Unlike the chicken wing muscles, the muscles in the drumstick are relatively easy to pry apart from one another and examine separately. If you start from the ankle, you might be able to produce something like this:

A chicken's drumstick with the muscles pried apart, showing the array of muscles and tendons
A Disassembled "Puppetmaster"

There is a tough band of cartilaginous material around the ankle, which I assume corresponds to the retinacula around human wrists and ankles, and which contains passages through which tendons slide, much like the carpal tunnel in the human wrist. If you cut this and pull it away, and then gradually pry, squeeze, or pull apart the muscles, you should find that the drumstick is indeed constructed like a "puppetmaster", with a bundle of muscles, each pulling on a "drawstring", each running out to the foot to pull the toes into different positions. The drumstick muscles are the engines that pull on the tendons and drive the motions of the foot. Your forearms and lower legs are presumably built in the same way inside.

I have read that, if you work carefully and pay close attention as you pull the muscles of the leg apart, you should be able to discover such minute things as blood vessels, nerves, and synovial bursae. However, I haven't had much luck finding these myself. (There are some tubes that are quite easy to notice, as they are filled with red blood. I believe these are veins, rather than arteries, because the arteries are muscular and allegedly contract upon death, squeezing the blood out of them...but I'm not at all positive about this. Are there any medical students or medical examiners out there who can confirm that in cadavers, veins are full and arteries are empty?)

If you remove all muscle as much as you can down to the bone, you will find the skeleton of the chicken leg:

A chicken leg quarter with the meat removed, showing the femur, knee, tibia, and fibula
The Bones of a Chicken Leg

As with the resemblance of chicken wing to human arm, the resemblance of chicken leg to human leg is more than skin deep. The thigh contains a single large bone, which we may as well call the femur. The lower leg contains a pair of long bones, one of which is large and strong (the tibia), and the other of which is thin and frail and stuck to the first (the fibula). In a human, the fibula is a secondary "helper" bone, but at least it is still as long as the entire lower leg, and is stuck firmly to the tibia at both ends. In a chicken, the fibula is so meager that it doesn't even reach the ankle end. It is just a needle sticking down from the knee joint.

The resemblance continues if we examine the joints in more detail. The knee has a cartilagenous covering over the front, resembling a kneecap, and it has vertical ligaments on the sides of the knee, and criss-cross ligaments inside, that resemble the collateral and cruciate ligaments in a human knee. The hip is a ball-and-socket joint consisting of the rounded upper end of the femur fitting into a socket in the hip bone. Several ligaments hold the bones together, including a ligament within the socket, helping to hold the head of the femur inside the socket (the ligamentum teres).

A chicken's knee joint, showing the collateral and cruciate ligaments
The Knee Joint
A chicken's hip joint, opened to show the head of the femur
The Head of the Femur

Since chicken quarters are apparently normally produced by sawing the hipbone from the rest of the body, and since this cut apparently normally goes through the spine, your chicken quarter might also give a nice view of a longitudinal section of a spine.

A cross-section of a chicken's spine, with attached femur and tibia
A Cross-Section of the Spine

Comments