The Digestive System of a Red Earthworm (Lumbricus rubellus)
The digestive system of an earthworm, like many other animals, starts from the mouth. From there there is a straight tube to the anus where the digestion of the food, such as dirt, occurs. After the worm eats its food (usually dirt) this food travels down to the pharynx, which acts as a suction pump, drawing in food. In the pharynx, the worm's glands secrete mucus to help digest the food more easily. The food then moves to the esophagus where it is mixed with calcium to neutralize the acidic pH of the food/mucus mixture. Then, the food travels to the crop, which acts as a temporary storage system for the worm's food. The food then moves down to the gizzard, where the food is ground into smaller particles, using chemicals secreted by glands (since the worm has no teeth). This now thick paste of food moves to the intestine where bacteria break it down, and take what nutrients are needed by the worm, and leave the rest to keep going down the digestive tract. Finally, the waste reaches the end point, the anus, where it is excreted from the worm's body in pellets called casts. These casts are so rich in nutrients that they can actually help us fertilize our soil to grow crops and plants!