It's easy to overlook the pieces and parts of the creepy-crawly earthworm. These slithering creatures are so far removed from humans it's difficult to fathom they have anything in common with us. However, like you, an earthworm eats and digests his food—but he has no stomach to help the process.
It All Starts with Food
A guy's gotta eat, even if he is an earthworm. Though he doesn't have teeth, the earthworm has a strong, muscular mouth, located at the front of his body. As he crawls through the soil, the earthworm sucks in his food. The pharynx helps in this process, acting like a vacuum to pull food into the worm's mouth. It also secretes fluid into the food. Just as a person has an esophagus, so does an earthworm, and the organ does the same thing in both people and worms: it serves as a passage allowing food to travel from the mouth to the next step in the digestive process.
Breaking It Down
The earthworm doesn't have a stomach, but like a bird he does have a crop, which is the place where his food is held before it makes its way to the gizzard. The gizzard goes to work, using its natural muscular action and fine grains of sand or rock to squeeze and grind the food completely. The intestine completes the digestive process, chemically digesting what's passed along from the gizzard and allowing the bloodstream to absorb usable nutrients. Of course, not everything is usable and an earthworm has to poop too, so undigested matter comes out of his anus.
What Goes In...
Since an earthworm's mouth is so small, he can eat only very small things, including many you can't see with your naked eye. You can't see the fungi, bacteria and protozoa he eats, but rest assured, the earthworm gets nutrition from them. He also eats plant matter and decaying animals. If something's a bit too large for the worm's tiny mouth, he will moisten his target to make it soft enough to suck into his mouth.
...Must Come Out
When the earthworm's through digesting his dinner, the poop that comes out is known as castings. Castings are moist and dark and high in nutrients gardeners love. Plants respond well to the nutrients in castings—so well, in fact, that some gardeners use castings as garden fertilizer. In addition to the natural fertilizing the earthworm provides, he also aerates the soil as he tunnels through the ground, giving improved access to water, air and nutrients deep into the soil, another boon for plants.
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