  Digestion in the small intestine is the result of complex mechanical and
biological phenomena which can be modelled at different scales. In a previous
article, we introduced a system of ordinary differential equations for
describing the transport and degradation-absorption processes during the
digestion. The present article sustains this simplified model by showing that
it can be seen as a macroscopic version of more realistic models including
biological phenomena at lower scales. In other words, our simplified model can
be considered as a limit of more realistic ones by averaging-homogenization
methods on biological processes representation.
