Surfactant is a mixture of dipalmitoilphosphatidylcholine (DPPC), other lipids and proteins .It is produced by type II alveolar epithelial cells . Lamellar bodies, membrane bound organelles containing whorls of phospholipids are formed in these cells and secreted into the alveolar lumen by exocytosis. Tubes of lipid called tubular myelin form from the extruded bodies , which in turn the phospholipid film 

The protein part of surfactant contain four unique proteins , SA-A , AP-B , SP-C , and SP-D.SP-A and SP-D are glycoproteins and SP-A is probably involved in the re-uptake of surfactant by type II cells .SP-B and SP-C are small proteins , which facilitate the formtion of mono-molocular film of phospholiipd. In fact the surfactant apoproteins and calcium ions are necessary for the effective and quick spread of the DPPC over the fluid surface of the alveoli. 

Some surfactant is taken up by the alveolar macrophage but more is taken up by endocytosis in type II ephithelial cells .Some of the protein lipd complaxes in surfactant taken up by these cells are recycled .