The beak moistens food with Saliva. Food is not chewed.
The esophagus takes the food down to the crop to be stored. After a chicken has eaten, the crop will feel full and bulge.
Food from the crop slowly passes down to the proventriculus.
The proventriculus mixes the food with acids and digestive enzymes.
Food is then passed through to the gizzard where insoluble (flint) grit has accumulated.
Food is ground down by strong muscular action in the gizzard.
From the gizzard, food is passed through to the small intestine and is reduced further with enzymes from the pancreas.
Bile produced by the liver and stored in the gall bladder helps to break down fat.
The intestines digest the food, taking nutrients from it.
Water and the remaining undigested food is absorbed in the large intestine.
The caeca are a pair of tubes that allow fermentation of undigested food to take place. This is emptied every 24 hours or so and is a light brown (mustard colour) froth. This can often be confused as diarrhea by the novice.
The cloaca / vent passes a combination of feces and urine, together with eggs from the oviduct.