Final answer:
Pressure gradients between the atmospheric pressure and the pressures inside the lungs drive pulmonary ventilation, adhering to Boyle's law. During inhalation, air enters the lungs when intra-alveolar pressure is lower than atmospheric pressure, whereas during exhalation, air exits as intra-alveolar pressure becomes higher. Transpulmonary pressure maintains lung inflation throughout the breathing cycle.
Step-by-step explanation:
Pulmonary ventilation is facilitated by the establishment of pressure gradients between the atmosphere and the lungs. During inhalation, atmospheric pressure (Patm) is greater than the intra-alveolar pressure (Palv), causing air to flow into the alveoli.
The difference between the intra-alveolar pressure and the intrapleural pressure (Pip) is known as the transpulmonary pressure, which keeps the lungs inflated. Boyle's law dictates that as the volume of the thoracic cavity increases during inhalation, the pressure within decreases, allowing air to enter the lungs. During exhalation, the process is reversed; the thoracic cavity volume decreases, and intrapulmonary pressure rises above atmospheric pressure, driving air out of the lungs.
Additionally, factors such as gravity can affect pressure gradients in the lungs, leading to anatomical shunts where there may be an imbalance in the ventilation and perfusion of the lungs, impacting gas exchange efficiency.