Q What is the difference between an incomplete digestive and a complete digestive system system? How are these types of digestive tubes associated or not to extracellular digestion?

Animals with an incomplete digestive system are those in which the digestive tube has only one opening platyhelminthes, cnidarians. Animals with a complete digestive system are those in which the digestive tube has two openings, anus and mouth all other animal phyla, with the exception of poriferans, that do not have any digestive tube.

In animals with incomplete digestive tubes the digestion is mixed it begins in the extracellular finishes and space in the intracellular space, in animals with complete digestive systems extracellular digestion within the digestive tube predominates.