Final answer:
During inspiration, the intrapulmonary pressure becomes lower than atmospheric pressure to allow air to flow into the lungs. This negative pressure is essential for driving pulmonary ventilation and is influenced by the volume changes in the chest cavity, as explained by Boyle's Law.
Step-by-step explanation:
To accomplish inspiration, the intrapulmonary pressure becomes lower than the atmospheric pressure. This process, often referred to as negative pressure breathing, involves the creation of a pressure gradient which drives pulmonary ventilation. According to Boyle's Law, as the volume of the chest cavity increases, intra-alveolar pressure decreases, allowing air to flow from an area of higher pressure (the atmosphere) to an area of lower pressure (the alveoli).
Intrapleural pressure also plays a significant role in breathing. It is always maintained at a negative value relative to both intrapulmonary and atmospheric pressure. This constant negative intrapleural pressure is critical in keeping the lungs expanded, which is necessary for efficient gas exchange during the breathing cycle.