What is the outcome when the lung's intrathoracic space increases during inhalation?

During inhalation, the intrathoracic space increases due to the contraction of the diaphragm and the expansion of the intercostal muscles, leading to a decrease in intrathoracic pressure compared to the atmospheric pressure outside the body. This pressure differential causes air to be drawn into the lungs, as air naturally flows from areas of higher pressure to areas of lower pressure. Therefore, the outcome of an increased intrathoracic space during inhalation is that air is effectively forced into the lungs, filling the alveoli where gas exchange occurs.

The other outcomes mentioned do not directly relate to the mechanical process occurring during inhalation. The expulsion of air from the lungs occurs during exhalation, not inhalation. Cellular respiration, which involves the consumption of oxygen and production of carbon dioxide, happens at the cellular level and is not a direct result of intrathoracic pressure changes during inhalation. Filtering of carbon dioxide from the air does not occur in the same way; instead, carbon dioxide is a byproduct of metabolism that is expelled from the body when we exhale.