The link between osmosis and diffusion and how they apply to the digestive system can be found in the large and small intestine:
In the small intestine, you can find substances such as nutrients or which get digested and down food is absorbed into the villi, and from there diffuse into the bloodstream which carries nutrients around the body.
The large intestine is where osmosis takes place. Water (and other liquids) pass through the large intestine and filters through to the bloodstream through osmosis.
