A cartilaginous structure at the bifurcation that produces sound in birds.

The opening into the trachea.

A chicken has air sacs connecting the lungs to the pneumatic bones, they act like bellows to pull the air into the lungs.

It takes two full breaths for air to move the whole way through the body of a chicken. The air moves first into the caudal air sacks, then to the lungs, then to the anterior air sacks and back out of the mouth (beak.)

Birds lack a diaphragm and instead lower their sternum as they inhale and lift their sternum as they exhale. The movement of the sternum is what changes the space of the thoracic cavity. With a greater amount of space the lungs and air sacs can fill and with less space that air is pushed out by way of the oral cavity.

Birds (chickens) have nine air sacks, doubling up on cervical, anterior thoracic, posterior thoracic and abdominal air sacks. However they only have one interclavicular sack.

The chicken is very unique (in contrast to mammals) in that they do not have any residual air left in their lungs after the commencement of their ventilation cycle. Another characteristic specific to chickens is that they use their syrinx to produce noise. With distinction to humans who utilize their larynx in order to produce sound.