From the esophagus down, mostly a mystery...stomach, small intestine (notably where bile, the poop-tint is added), colon, rectum. Lots of mucus-oozing cells keep things squishy; lots of peristaltic waves of smooth muscle keep things moving. Enzymes and acid do their stuff; most of the nutrition is absorbed in the 33 feet of small intestine; most of the water is reclaimed in the 7 or so feet of large intestine. Diversion of blood can lead to food coma.