Final answer:
Pulmonary ventilation includes inspiration and expiration, influenced by the diaphragm and intercostal muscles, with changes in lung pressures described by Boyle's Law. Graphs would show intra-alveolar pressure and volume of air moved fluctuating with breathing cycles, and intrapleural pressure staying negative but varying in magnitude.
Step-by-step explanation:
Pulmonary ventilation consists of two phases: inspiration (inhalation) and expiration (exhalation). During inspiration, the diaphragm and external intercostal muscles contract, enlarging the thoracic cavity and decreasing intra-alveolar pressure below atmospheric pressure, resulting in air inflow. Conversely, during expiration, relaxation of these muscles allows the lungs and thoracic cavity to recoil, increasing intra-alveolar pressure above atmospheric pressure, and air is expelled.
Boyle's Law states that in a closed system, pressure and volume of a gas are inversely related, which helps to explain the changes in lung pressures during breathing cycles. When lung volume increases during inspiration, intra-alveolar pressure falls; when it decreases during expiration, intra-alveolar pressure rises. The intrapleural pressure remains negative relative to atmospheric pressure, ensuring the lungs do not collapse.
Graphs depicting these changes would show: (A) intra-alveolar pressure dipping below atmospheric pressure during inspiration and rising above it during expiration, (B) intrapleural pressure being consistently negative but becoming more negative during inspiration, and (C) the volume of air moved increasing with inhalation and decreasing with exhalation.