Final answer:
Intrapulmonary pressure refers to the pressure within the alveoli of the lungs, equal to atmospheric pressure during rest, while intrapleural pressure is the pressure within the fluid-filled pleural cavity, always negative compared to atmospheric pressure. This pressure difference allows for the lung expansion and contraction necessary for breathing.
Step-by-step explanation:
The distinction between intrapulmonary pressure and intrapleural pressure lies in where the pressure is exerted. Intrapulmonary pressure is the pressure within the lungs, specifically within the alveoli, while intrapleural pressure is the pressure within the pleural cavity, which is the thin fluid-filled space between the two layers of the pleura surrounding the lungs.
Intrapulmonary pressure, also known as intra-alveolar pressure, changes with the phases of breathing, similar to intrapleural pressure, but is typically equal to atmospheric pressure at rest. On the other hand, intrapleural pressure is always lower (or negative compared to atmospheric pressure). To facilitate breathing through pulmonary ventilation, air flows down the pressure gradient, filling the lungs when intrapulmonary pressure is lower than atmospheric pressure during inhalation, and exiting when it's higher during exhalation. The difference between intrapleural pressure and intrapulmonary pressure, known as transpulmonary pressure, is crucial as it keeps the lungs expanded and prevents them from collapsing.