What change occurs in thoracic volume during exhalation?

• A. It increases
• B. It decreases
• C. It stays the same
• D. It fluctuates constantly

Answer: (B)

During exhalation, the thoracic volume decreases. This process begins when the diaphragm and intercostal muscles relax, causing the chest cavity to contract. As the volume within the thoracic cavity decreases, the pressure inside it increases, leading to air being expelled from the lungs.

This reduction in volume is crucial because it facilitates the flow of air out of the respiratory system. The mechanics of exhalation are part of a larger cycle of breathing, where the movements of the skeletal muscles and changes in thoracic pressure play a vital role in gas exchange. Understanding this relationship between thoracic volume and pressure is fundamental to grasping how ventilation operates effectively in the body.