How does a chicken folds its wing closed and how it spreads open?

A chicken's wing is a complex structure made up of several bones, muscles, and joints. When a chicken folds its wing closed, several things happen:

1. The elbow joint, which connects the upper and lower arm bones, bends.

2. The wrist joint, which connects the lower arm bone to the bones of the hand, also bends.

3. The primary flight feathers, which are the large feathers on the outermost part of the wing, fold over and overlap each other.

4. The secondary flight feathers, which are the smaller feathers closer to the body, also fold over and overlap each other.

When a chicken spreads its wing open, the opposite of these actions occurs:

1. The elbow and wrist joints straighten.

2. The primary and secondary flight feathers spread out and fan out.

The muscles that control the wing movements are located in the shoulder and chest. When the chicken contracts these muscles, it causes the bones and joints of the wing to move.

In addition to the muscles, there are also ligaments and tendons that help to stabilize the wing and control its movements. These structures work together to give chickens the ability to fly, flap their wings, and perform a variety of other movements.