We at Mental Floss write a lot about poop, but not as often about how our bodies produce the stuff in the first place. Humans eat between two and six pounds of food per day—and as TED-Ed’s latest video explains, this grub passes through an elaborate network of channels, organs, tissues, and nerves that’s commonly known as the human digestive system.

The digestive system is the unsung hero of our torso. Its 10 organs—which include the esophagus, liver, intestines, and stomach—contain over 20 specialized cell types, and the gastrointestinal track alone has an internal surface area of between 320 and 430 square feet. But the digestive process doesn’t begin and end with the esophagus—it starts in our mouths.

The body produces just over six cups of saliva per day, a process that begins when we start salivating over a tasty morsel. This clear substance contains starch-busting enzymes, which break the food we eat into a moist lump (a bolus) that will eventually become the stuff that comes out our other ends. In all, this journey lasts between 30 and 40 hours—and you can follow it step by step by watching TED-Ed’s video below.