Final answer:
During exhalation, the thoracic cavity volume decreases, and the intrathoracic pressure increases, aiding in the return of blood to the heart.
Step-by-step explanation:
When we exhale, the thoracic cavity volume decreases and intrathoracic pressure increases, placing pressure on vessels within the thoracic cavity to help return blood to the heart.
The process of exhalation is essentially passive, with the diaphragm and intercostal muscles relaxing, leading to the thoracic cavity and lungs diminishing in size, and a subsequent increase in intrapulmonary pressure. This pressure forces air out of the lungs similarly to how air is expelled from a deflating balloon.
During exhalation, the thoracic cavity volume decreases and intrathoracic pressure increases, which places pressure on vessels within the thoracic cavity to help return blood to the heart.