The first step in the digestive process happens before we even taste food. Just by smelling that homemade apple pie or thinking about how delicious that ripe tomato is going to be, you start salivating — and the digestive process begins in preparation for that first bite.
Almost all animals have a tube-type digestive system in which food:
enters the mouth
passes through a long tube
exits the body as feces (poop) through the anus
Along the way, food is broken down into tiny molecules so that the body can absorb nutrients it needs:
Protein must be broken down into amino acids.
Starches break down into simple sugars.
Fats break down into into fatty acids and glycerol.