Which of the following structures is responsible for ventilation of the lungs?

The diaphragm plays a crucial role in the process of ventilation, which is the movement of air into and out of the lungs. This dome-shaped muscle separates the thoracic cavity from the abdominal cavity and is primarily responsible for increasing and decreasing the volume of the thoracic cavity during breathing.

When the diaphragm contracts, it moves downward, enlarging the thoracic cavity's volume and creating a negative pressure that pulls air into the lungs (inhalation). Conversely, when the diaphragm relaxes, it moves upward, reducing the thoracic cavity's volume, which increases the pressure inside the lungs and forces air out (exhalation). This muscle's unique function makes it a key component in the respiratory process.

While the intercostal muscles also assist in ventilation by raising and lowering the rib cage during breathing, their role is secondary to that of the diaphragm. The thoracic cavity itself is the space where the lungs are located and does not actively participate in ventilation. A spirometer is a tool used to measure lung volumes and flow, but it does not play a role in the physical act of ventilation.