Final answer:
Thoracic wall compliance affects the ability to breathe; the diaphragm and intercostal muscles contract during inhalation, expanding the thoracic cavity, and relax during exhalation, decreasing its volume and expelling air.
Step-by-step explanation:
Thoracic wall compliance is a key factor in the process of breathing, as it determines the ability of the thoracic wall to stretch under pressure and therefore affects how the thoracic cavity and lungs expand and contract. During inspiration (inhaling), the diaphragm contracts and flattens while the external intercostal muscles lift the rib cage, increasing the thoracic cavity's volume and reducing the pressure inside the pleural cavities. This pressure decrease allows air to flow into the lungs.
Conversely, during expiration (exhaling), the diaphragm and intercostal muscles relax, the thoracic cavity shrinks, and the resulting increase in pressure forces air out of the lungs. The combined actions of the diaphragm and intercostal muscles are critical in changing the volume-pressure dynamics within the thoracic cavity to facilitate pulmonary ventilation.