Final answer:
Inspiration involves the contraction of external intercostal muscles, which raises the rib cage and lowers internal lung pressure, causing air to flow in. These muscles, along with the internal intercostal muscles and the diaphragm, facilitate the process of pulmonary ventilation or breathing.
Step-by-step explanation:
Inspiration and the Role of the External Intercostal Muscles
- During inspiration or inhalation, the external intercostal muscles contract, pulling the rib cage upward and outward. This action increases the volume inside the thoracic cavity and the pleural cavities, creating a lower pressure within the lungs compared to the atmospheric pressure. Consequently, air flows into the lungs to equalize the pressure, allowing the lungs to inflate. Conversely, the internal intercostal muscles are responsible for expiration, by which they help compress the rib cage during exhalation. Pulmonary ventilation is thus the interplay between these muscle groups and the diaphragm, facilitating the essential process of breathing.