What occurs in the lungs during inspiration?

During inspiration, the diaphragm contracts and flattens, which increases the volume of the thoracic cavity. This action creates a negative pressure within the lungs, allowing air to rush in from the external environment. Additionally, the intercostal muscles between the ribs also contract, causing the ribs to elevate. This coordinated movement further expands the chest cavity, enhancing the airflow into the lungs.

The diaphragm's flattening and the elevation of the ribs are crucial for facilitating the inhalation process, ensuring that sufficient air enters the lungs to meet the body’s oxygen requirements. This process contrasts with the actions of expiration, where air is expelled from the lungs. The other options either misrepresent the physiological processes involved in respiration or pertain to unrelated concepts, like the absorption of gases by villi, which is more applicable to the gastrointestinal system rather than the respiratory system.