Michelle Koo's Anatomy and Physiology Blog: Chicken Dissection Analysis

In our chicken dissection, we observed the exterior and interior parts of our chicken, paying attention to how the muscles, tendons, and bones help the chicken move. First, we peeled off the skin on the breast and made an incision down the midline of the pectoralis major in order to expose the pectoralis minor underneath. The pectoralis major allows the bird to fly by pulling on its wing when it contracts. As seen in the picture below, the pectoralis minor is directly under the pectoralis major and it pulls the wings dorsally when flying.

Pectoralis major and pectoralis minor, orbicularis shaped
muscles that make up the chicken´s breast

The trapezius muscle and latissimus dorsi
which is a depressor for the chicken´s wing

Next, we flipped the chicken over with the posterior side facing up, peeled off the skin, and observed the trapezius and the latissimus dorsi. Looking at the picture, you can see the trapezius runs from the backbone to the shoulder, which allows the chicken to pull their shoulder back. The lattissimus dorsi are distal to the chicken's back, stretching form the spine to an origin of a wing.

Deltoid: piriformis muscle on top of shoulder

We then detached the wings from the chicken and observed the movement in the deltoid, biceps brachii, and triceps humeralis. Similarly in humans, the deltoid located at the top of the shoulders helps to raise the upper arm (or wing). Attached below on the upper arm, the biceps brachii flexes the arm with a concentric contraction, shortening the muscle. As the biceps brachii contract, the tripceps brachii, located on the inferior side of the arm relaxes. When one contracts the other relaxes and vice versa. The femur is the bone underneath these two muscles with its origin at the deltoid and its insertion at the humerous. When the biceps brachii contracts, the insertion point (humerous) moves closer to the origin (deltoid). The flexor carpi ulnaris runs from the bottom tip of the humerous (elbow) across the ulna towards the far end of the chicken's hand.

Brachioradialis: Largest muscle on lower wing,
located on the lateral side of hand, same side as the radius.
Flexor carpi ulnaris: On posterior side of wing,
from "pinky" to elbow

Biceps brachii and triceps brachii located on
the anterior and posterior sides of the
chicken's upper wing

While observing the upper wing, we discovered that by twisting the humerous, the wing flexes back and forth demonstrating extension and flexion.

Check out the video below to see the movement!

Since these chicken's were raised to be eaten as meat, their thighs and calves are very disproportionate, often making the muscles on their calves much larger than their quadriceps. Shown below is the sartorius and quadriceps femoris. The sartorius is located down the front length of the thighs and allows both chickens and humans to cross their legs. The quadripceps femoris, located on the inner thigh is made up of 4 different muscles that flex and extend the lower leg. In humans, it is known as the rectus femoris and the muscle helps to extend the knee joint and is crucial for walking/running/jumping.

Sartorius and Quadricep femoris: located on
the thigh to help with crossing of legs and
extension of lower leg

The illiotibialis, seen in the picture to the right is covers
the majority of the thighs and
allows for extension and flexion of the leg

The biceps femoris is a part of the hamstring group, and allows the bird to flexes its leg. In humans, we exercise and use this muscle when doing leg curls. The semimembranosus is inferior and medial to the biceps femoris and extends the thigh. The semitendinosus is anterior and medial to the semimembranosus, on the interior region of the thigh muscle.

Peroneus longus: Maximus muscle on drumstick side
of leg.
Tibilais anterior: Major muscle to peroneus longues
Runs along tibia in front area of lower leg, flexes foot