Final answer:
The diaphragm and the external intercostal muscles are used to enlarge the chest cavity during pulmonary respiration.
Step-by-step explanation:
During pulmonary respiration, two major muscles are used to enlarge the chest cavity and facilitate breathing. These muscles are the diaphragm and the external intercostal muscles. When the diaphragm contracts, it moves downward, creating a larger space in the thoracic cavity. The external intercostal muscles contract as well, causing the ribs to move upward and outward, further expanding the thoracic cavity.