There are a number of types of<unk>  available. Like their natural counterparts,<unk> preparations consist of phospholipids (mainly DPPC) combined with spreading agents such as SP-B and SP-C. Ex-situ measurements of surface tension and interfacial rheology can help to understand the functionality of<unk> . Synthetic<unk> : * Colfosceril palmitate (Exosurf) - a mixture of DPPC with hexadecanol and tyloxapol added as spreading agents * Pumactant (Artificial Lung Expanding Compound or ALEC) - a mixture of DPPC and PG * Lucinactant (KL-4) - composed of DPPC, palmitoyl-oleoyl phosphatidylglycerol, and palmitic acid, combined with a 21 amino acid synthetic peptide (sinapultide) that mimics the C-terminal helical domain of SP-B. * Venticute - DPPC, PG, palmitic acid and recombinant SP-C * Lucinactant (trade name Surfaxin) is a liquid medication that contains DPPC, POPG as the sodium salt, and palmitic acid. Animal derived<unk> s: * Beractant * (Alveofact) - extracted from cow lung lavage fluid, manufacturing by Boehringer Ingelheim * (Survanta) - extracted from minced cow lung with additional DPPC, palmitic acid and tripalmitin, manufacturing by Abbvie * (Beraksurf) - extracted from minced cow lung with additional DPPC, palmitic acid and tripalmitin, manufacturing by Tekzima * Calfactant (Infasurf) - extracted from calf lung lavage fluid * Poractant alfa (Curosurf) - extracted from material derived from minced pig lung
Pulmonary surfactant 
Hyalobarrier
Bruch's membrane
Fluid compartments
Reticular membrane
Schneiderian membrane
Neurotrophic factors
Endobronchial valve