Digestion is the breakdown of food by a living organism into chemically
simpler forms that can be readily assimilated (see assimilation)
and absorbed by the body. It requires the action of digestive enzymes.
It most animals, digestion is an extracellular process. In mammals, in particular,
it involves the gastrointestinal
tract, which, together with accessory structures, such as the teeth,
pancreas, and gall
bladder, makes up the digestive
system. In simpler organisms, such as protozoans
and cnidarians, digestion is primarily
intracellular, for example involving phagocytic cells.
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