What role does the thoracic cavity play during breathing?

The thoracic cavity plays a crucial role in the mechanics of breathing through the creation of pressure changes that facilitate airflow into and out of the lungs. During inhalation, the diaphragm and intercostal muscles contract, increasing the volume of the thoracic cavity. This increase in volume leads to a decrease in air pressure inside the cavity relative to the outside atmosphere, prompting air to flow into the lungs.

Conversely, during exhalation, these muscles relax, causing the volume of the thoracic cavity to decrease. This decrease in volume results in an increase in pressure, which forces air out of the lungs. This process of creating pressure changes is fundamental to ventilation and is critical for maintaining adequate gas exchange in the respiratory system.

The other options, while related to respiration, do not accurately describe the primary function of the thoracic cavity during breathing. For example, filtering air is primarily the function of nasal passages and the respiratory epithelium, while adjusting oxygen levels and removing carbon dioxide are processes that occur at the level of the alveoli and do not directly involve the thoracic cavity's structural role in airflow.