How do the lungs facilitate breathing?

The lungs facilitate breathing primarily by contracting and expanding. During inhalation, the diaphragm and intercostal muscles contract, leading to a decrease in pressure within the thoracic cavity. This creates a vacuum effect, allowing air to flow into the lungs. Conversely, during exhalation, these muscles relax, and the elastic recoil of the lung tissue occurs, pushing air out of the lungs. This dynamic process of contraction and expansion is essential for the exchange of oxygen and carbon dioxide in the alveoli, where gas exchange occurs.

In contrast, filtering blood is a function of the kidneys and not the lungs. Producing sound is related to the vocal cords and the structures of the larynx rather than the lung function itself. Pumping oxygen is not accurate as the lungs are involved in gas exchange but do not actively pump gases; the heart is responsible for pumping blood that carries oxygen throughout the body. Thus, the mechanism of contraction and expansion is fundamental to the respiratory process.