Final answer:
The lungs appear collapsed in the fetus due to amniotic fluid and the presence of the placenta supplying oxygenated blood. The newborn takes its first breath and inflates the lungs after birth.
Step-by-step explanation:
The lungs appear collapsed in the fetus due to several factors. First, during gestation, the lungs are filled with amniotic fluid which causes them to be partially collapsed. Additionally, there is no need for the fetus to breathe because the placenta supplies it with oxygenated blood. It is only when the baby is born and experiences a decrease in oxygenated blood flow and an increase in carbon dioxide levels that it triggers the newborn to take its first breath and inflate the lungs.