Extracellular digestion

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.