Final answer:
The diaphragm is the primary muscle that drives ventilation, contracting to create negative pressure in the lungs for inhalation.
Step-by-step explanation:
One of the primary muscles that drives ventilation is the diaphragm. This large, dome-shaped muscle separates the thoracic (chest) and abdominal cavities. When we inhale, the diaphragm contracts, causing the thoracic cavity to expand, which in turn lowers the pressure in the lungs compared to the outside air, causing air to flow into the lungs. Additionally, the external intercostal muscles between the ribs assist by expanding the ribs outward.