Final answer:
The alveoli are lined with a phospholipid compound called pulmonary surfactant, which is secreted by type II alveolar cells. It significantly reduces surface tension in the alveoli to prevent collapse and maintain lung function, playing an essential role in gas exchange.
Step-by-step explanation:
The alveoli, which are essential for gas exchange in the respiratory system, are lined with a phospholipid compound known as pulmonary surfactant. This surfactant is secreted by type II alveolar cells and consists of phospholipids and proteins. Its primary function is to reduce the surface tension within the alveoli, thus preventing their collapse during exhalation and maintaining better lung function.
Surfactant facilitates efficient gas exchange by lowering the surface tension at the air-tissue interface of the alveoli. This allows the alveoli to remain open, making it easier for oxygen to diffuse into the blood and for carbon dioxide to be expelled from the blood into the alveoli. The presence of surfactants in our alveoli is a critical aspect of healthy respiratory and pulmonary function.
Without surfactant, the high surface tension caused by the alveolar fluid would lead to the collapse of the alveoli, a condition known as atelectasis. By modulating surface tensions, surfactant ensures that both small and large alveoli can function properly and efficiently participate in oxygen and carbon dioxide exchange during respiration.