Although they do not have a network of veins and arteries like mammals do,
most insects do a have a simple open circulatory system which
consists of a heart and an aorta.
Unlike human blood, insect blood carries nutrients only, not
oxygen, and thus it is yellow or green in color. The blood of an insect fills its body
cavity and surrounds its internal organs. The blood enters a tube with holes in it
which runs lengthwise along the body and collect blood. This tube has
valves over these openings to prevent backflow. The insect's
heart pumps the blood out of the aorta
where it supplies nutrients to the head and brain, then it
flows to the rest of the body.
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