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hearts

An earthworm has five pair of muscles, or hearts, around the esophagus that are sometimes referred to as aortic arches. Since an earthworm has a closed circulatory system that recirculates unused blood, a powerful pump is required. Blood is oxygenated in the dorsal blood vessel by the moist soil that surrounds the worm. This blood is then pumped to other parts of the body thanks to the hearts.