Alveoli are the spherical outcroppings of the respiratory bronchioles.<unk>  is a surface-active complex of phospholipids and proteins formed by type II alveolar cells. The proteins and lipids that make up the<unk>  have both hydrophilic and hydrophobic regions. By adsorbing to the air-water interface of alveoli, with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of<unk> , dipalmitoylphosphatidylcholine (DPPC), reduces surface tension. As a medication,<unk>  is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.
Pulmonary surfactant
Hyalobarrier
Bruch's membrane
Fluid compartments
Reticular membrane
Schneiderian membrane
Neurotrophic factors
Endobronchial valve