Answer:
Effective breathing is made possible by the widest part of the bony thorax, which is between the eighth and ninth ribs. This region is vital in facilitating chest cavity expansion and contraction.
Step-by-step explanation:
When we inhale, the intercostal muscles between the ribs tighten and lift the ribcage while the diaphragm contracts and slides downward. The chest cavity widens as a result of this motion, allowing the lungs to fill with air. The wider part of the bony thorax allows the ribs to extend farther, increasing the chest cavity's overall volume.
On the other hand, during exhalation, the intercostal muscles relax and let the ribcage slide inside as the diaphragm relaxes and rises. This motion facilitates lung airflow and reduces the size of the chest cavity.