Final answer:
Lung inflation is maintained by the contraction of the diaphragm and intercostal muscles, combined with the presence of surfactant that reduces surface tension within the alveoli.
Step-by-step explanation:
The content loaded lung inflation (non-collapse) is maintained primarily by the mechanics of the respiratory muscles and the presence of a substance known as surfactant. Lung inflation relies on the actions of the diaphragm contracting and lowering and the intercostal muscles expanding the chest wall, which together reduce intra-pleural pressure and allow air to enter. Moreover, a mixture of phospholipids and lipoproteins, surfactant, acts to decrease the surface tension within the alveoli, allowing them to remain open and preventing collapse during exhalation. These combined processes ensure the lungs can efficiently exchange oxygen and carbon dioxide without collapsing.
Surfactant: Surfactant is a substance produced by the type II alveolar cells in the lungs. It reduces the surface tension of the fluid lining the alveoli, making it easier for the alveoli to expand and preventing them from collapsing.
Negative Intrapleural Pressure: The pleural cavity, the space between the lung and the chest wall, normally has a negative pressure. This negative pressure helps keep the lungs inflated. When the chest expands during inhalation, the negative intrapleural pressure increases, pulling the lungs outward and preventing collapse.
Together, these mechanisms ensure that the lungs remain expanded and functional during the breathing process. If there is a disruption in either surfactant production or the negative pressure in the pleural cavity, it can lead to conditions such as atelectasis, where parts of the lung collapse.