Chicken Dissection

Last class, we did a chicken dissection in order to compare how similar the muscles of a chicken are to the muscles of a human. When we dissected the breast of the chicken, we found the pectoralis major and the pectoralis minor, which are shown in the image below. In birds, these two muscles, with the humerus and sternum, help lift the wing vertically and dorsally. This is extremely similar to the anatomy of humans, in which the pectoralis minor and major pull the shoulder up and down. Thus, we can see how the bones of the skeletal system and muscles in the muscular system help humans and animals move.

Pectoralis Major (white) - makes up the bulk of the breast muscle
Pectoralis Minor (yellow) - thin and triangular in shape

Many other similarities can be seen between the anatomy of a chicken and that of humans. In fact, many of the structures are homologous. The deltoid, biceps brachii, and the triceps humeralis, for example, are all structures involved in moving the wings of birds and also, similarly, are involved in moving the arms of humans. A third similarity can be seen in the flexor carpi ulnaris and brachioradialis of birds and humans, which aid in flexing and pulling back the hand.

Another important concept related to muscles that we learned is the origin and insertion of muscles. This can best be seen in the movements of the first wing segment/drumette of the chicken. The triceps humeralis works to straighten the arm or wing and the biceps brachii works in flexing the arm or wing. The chicken's upper arm also has the deltoid, which raises the arm. The origin of the arm is the shoulder, as that's where it attaches to the body. The insertion includes all the muscles that move in order to flex and extend the arm.

Deltoid (blue) - round and triangular muscle at the upper most part of the shoulder
Biceps brachii (green) - lies between the shoulder and the elbow
Triceps humeralis (white) - the main bone of the upper arm 

Some additional pictures from the chicken dissection and the functions of the muscles depicted are shown below:

Thigh (black)
Drumstick (blue)
Both aid in moving the legs 

Iliotibialis (red) - extends the thigh and flexes the leg

Sartorius (blue) - flexes the thigh, allowing the crossing of the knee
Biceps femoris (yellow) - flexes the leg
Semimembranosus (green) - extends the thigh
Semitendenosus (white) - extends the thigh
Quadriceps femoris (red) - flexes the thigh and extends the lower leg

Gastrocnemius (blue) - extends the foot and flexes the lower leg
Peroneus longus (black) - extends the foot
Tibialis anterior (yellow) - flexes the foot

Trapezius (yellow) - pull the shoulders back
Latissimus dorsi (green) - extend/pull the wing or arm