Final answer:
The three major parts of the circulatory system in earthworms are blood vessels, hearts, and blood.
Step-by-step explanation:
The circulatory system in earthworms consists of three major parts: the blood vessels, the hearts, and the blood.
The blood vessels in an earthworm are long and thin tubes that carry the blood throughout the body. There are two types of blood vessels: arteries that carry oxygenated blood away from the heart, and veins that carry deoxygenated blood back to the heart.
The earthworm has multiple hearts, typically five in total. These hearts act as pumps to circulate the blood throughout the body. The earthworm has a closed circulatory system, meaning that the blood is contained within the vessels and does not directly come into contact with the body tissues.