Which two organ systems develop last in a baby?

• A. Lungs and GI
• B. Heart and lungs
• C. Brain and spinal cord
• D. Kidneys and liver

Answer: (A)

Late maturation of organ systems necessary for independent life means the lungs and the gastrointestinal tract are among the last to complete development. The lungs must switch from relying on the placenta for oxygen to exchanging gases in air, which hinges on producing surfactant and forming functioning alveoli; this entire transition and the final fine-tuning of lung structure continue late in gestation and even after birth, making respiratory readiness a late-developing feature. The gastrointestinal tract also matures gradually, developing the ability to coordinate swallowing, digestion, and absorption of nutrients with the appropriate enzymes and bile after birth. In contrast, other systems like the heart and nervous system reach functional readiness earlier in gestation, though development continues after birth.