Prior to 1970s, many premature babies died because they could not breathe.
The lung tissue is glandular and the alveoli are collapsed.
Fetuses do undergo ventilation of amniotic fluid.
After the discovery of surfactant, the lives of many pre-term babies were saved.
Surfactant was injected into the amniotic fluid if a woman's premature labor could not be stopped.
The fetus would "inhale" the surfactant in the amniotic fluid.
When the fetus was delivered, it could successfully be ventilated because the surfactant allowed the alveoli to open.
In adults, every time we sigh, cough, sneeze, yawn or take a deep breath, surfactant is released from type II pneumocytes.