Final answer:
Pulmonary ventilation involves the inspiration phase where air enters the lungs due to the diaphragm contracting, and the expiration phase where air exits the lungs when the diaphragm relaxes.
Step-by-step explanation:
Respiratory Phases in Radiographic Imaging
Pulmonary ventilation includes two phases: inspiration and expiration. During inspiration, the diaphragm contracts and moves downward, while the external intercostal muscles cause the ribs to move upward and outward, expanding the thoracic cavity and reducing the intra-alveolar pressure, allowing air to flow into the lungs.
Conversely, during expiration, these muscles relax, and the thoracic cavity's size decreases, increasing the pressure and pushing air out of the lungs. In the context of radiographic imaging, it is crucial to instruct patients to hold their breath at the end of inspiration or expiration to obtain clear and diagnostic images.