Viscoelastic absorbed layer

Mucus serves as a lubricant and protective layer. Its most important property is its viscoelasticity, which enables it to act as a mechanical barrier, but also allows it to flow. The presence of a mucus layer has important implications for drag delivery. Mucus acts as a physical barrier through which drug molecules must diffuse, prior to reaching the absorbing surface. The rate of diffusion through the mucus will be dependent upon such factors as the thickness of the mucus layer, mucus viscosity and any interactions which may occur between the drag and mucus. 

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