Extracellular digestion is a process in which saprobionts feed by secreting enzymes through the cell membrane onto the food. The enzymes catalyse the digestion of the food into molecules small enough to be taken up by passive diffusion, transport or phagocytosis. These nutrients are transferred into the blood or other body fluids. Since digestion occurs outside the cell, it is said to be extracellular. It takes place either in the lumen of the digestive system, in a gastric cavity or other digestive organ, or completely outside the body.
Extracellular digestion is a form of digestion found in all saprobiontic annelids, crustaceans, arthropods, lichens and chordates, including vertebrates. 
^Advanced Biology Principles, p296, fig 14.16—Diagram detailing the re-absorption of substrates within the hypha.
^Advanced biology principles, p 296—states the purpose of saprotrophs and their internal nutrition, as well as the main two types of fungi that are most often referred to, as well as describes, visually, the process of saprotrophic nutrition through a diagram of hyphae, referring to the Rhizobium on damp, stale whole-meal bread or rotting fruit.
^Clegg, C. J.; Mackean, D. G. (2006). Advanced Biology: Principles and Applications, 2nd ed. Hodder Publishing