Final answer:
Expiration or exhalation is the process when air is rushed out of the lungs. This occurs as the diaphragm and intercostal muscles relax, leading to higher internal lung pressure that pushes air out.
Step-by-step explanation:
When air is rushed out of the lungs, it is called expiration or exhalation. The process of pulmonary ventilation includes expiration, which occurs when the diaphragm and intercostal muscles relax, leading to a decrease in the volume of the thoracic cavity. This increase in internal lung pressure forces air out of the lungs. During normal breathing, this process is passive but can involve active muscle contractions during forced expiration, such as when internal intercostals and abdominal muscles contract to expel air more forcefully.