At birth
Pig lungs.
Fetal lungs are not functioning; no organism can start to breathe while immersed in amniotic fluid. Lungs only begin to function at birth.
Lungs collect oxygen.
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.
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A fetal pig's lungs are collapsed because they are filled with fluid while in the uterus. This allows for easier passage through the birth canal and prevents the lungs from being damaged during development. Once the pig is born and takes its first breath, the lungs expand and fill with air.
smoothe
chest cavity
so pigs can breathe.
rib cage
Trachea