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Earthworm Digestive System
How earthworms digest their food.
An earthworm’s digestive system. Like all heterotrophs, earthworms cannot manufacture their food, but must eat and digest their food for energy.
An earthworm may appear crude and simple, but they are actually very complex.
The path of digestion begins at the mouth. An earthworm has a covering over the mouth called a prostomium which also acts as a wedge to help the earthworm move through the soil.
The next stop on the path of digestion is the pharynx. At the pharynx the food is lubricated with mucus in order for the dirt to move through the digestive tract.
From the pharynx, the dirt moves to the esophagus where chemical digestion occurs. Calcium carbonate is secreted into the food and starts breaking down the dirt as it moves through the esophagus.
Up next is the crop which is a storage area for the dirt before it moves to the gizzard.
The gizzard acts a little like teeth and the stomach. The dirt is ground up at the gizzard and digestive enzymes are added at the gizzard.
From the gizzard, the dirt, which is like a paste moves to the intestine. Inside the intestine bacteria break down the dirt mixture and blood vessels absorb important nutrients.
The end of the digestive journey ends at the anus with the earthworm pooping out the digested dirt. An earthworm’s poop is called casts.
Farmers and gardeners like these casts because they help fertilize the soil.