Pig lungs.
Lungs collect oxygen.
The pig has not yet used the lungs to breathe, so therefore they lungs have not been inflated and filled with air.
The main function of a pig's trachea is to breathe. It is part of system of passages that allow air into the lungs.
When the lungs do not function the backup respiratory system takes over the function of the lungs. This is true in a fetal pig.
If the umbilical cord is not cut off it will deteriorate after the pig makes full use of its lungs. The pig uses its lungs immediately after it is born.
chest cavity
At birth
smoothe
rib cage
Trachea
so pigs can breathe.