Which process occurs during inhalation?

During inhalation, the primary actions involve the contraction of the intercostal muscles and the diaphragm. When the intercostal muscles contract, they elevate the rib cage, increasing the volume of the thoracic cavity. Simultaneously, the diaphragm, which is a dome-shaped muscle at the base of the thoracic cavity, contracts and moves downward. This combined action creates a negative pressure in the lungs compared to the atmospheric pressure, allowing air to flow into the lungs.

The other options do not accurately describe the mechanics of inhalation. For instance, if the intercostal muscles were to relax while the diaphragm descends, this would not effectively increase the thoracic cavity volume, leading to insufficient airflow into the lungs. Understanding these mechanics is crucial for grasping how breathing functions and the role of these muscles during the respiratory process.