In the second trimester, the fetus begins preparing for breathing through movement of which structures?

In the second trimester, the fetus begins preparing for breathing through movement of which structures?

• A. Diaphragm and chest muscles
• B. Lung alveoli
• C. Lung tissue maturation
• D. Heart and vessels

Answer: (A)

Fetal breathing movements are driven by the diaphragm and chest wall muscles. These structures contract and relax to expand and compress the thoracic cavity, allowing the fetus to “practice” breathing by moving air-filled lung fluid in and out. This rehearsal helps the lungs develop by stretching airways, promoting lung fluid clearance, and supporting maturation of the respiratory system—preparing the baby for air breathing after birth. Lung alveoli and tissue maturation are structural developmental processes, and the heart and vessels relate to circulation, not the breathing movements.

Fetal breathing movements are driven by the diaphragm and chest wall muscles. These structures contract and relax to expand and compress the thoracic cavity, allowing the fetus to “practice” breathing by moving air-filled lung fluid in and out. This rehearsal helps the lungs develop by stretching airways, promoting lung fluid clearance, and supporting maturation of the respiratory system—preparing the baby for air breathing after birth. Lung alveoli and tissue maturation are structural developmental processes, and the heart and vessels relate to circulation, not the breathing movements.